Perl Security

by affaan-mef648e01899ba3e8dc6371642deaaf64b4477775No license275K starsListed Oct 9, 2026Updated Oct 9, 2026Repository updated 4 days ago

Comprehensive Perl security covering taint mode, input validation, safe process execution, DBI parameterized queries, web security (XSS/SQLi/CSRF), and perlcritic security policies. Use when reviewing Perl input handling, process execution, DBI queries, or web-facing code.

Instructions onlySecurity Software Development

AI-generated overview

Guidelines for writing and reviewing secure Perl code, covering taint mode, input validation, DBI queries and web security.

What it does: Provides security guidance for Perl applications: taint mode and untainting patterns, allowlist input validation, ReDoS-safe regular expressions, safe file and process execution, DBI parameterized queries, and web protections such as XSS, CSRF and header hardening. It also lists perlcritic security policies and a review checklist with anti-patterns. It produces advice and code examples rather than files or scripts.
When to use it: Use it when reviewing or writing Perl code that handles user input, filesystem paths, shell commands, DBI queries or web-facing endpoints. It also fits security reviews of Perl web applications built on CGI, Mojolicious, Dancer2 or Catalyst.
Requirements: No scripts or tooling are bundled; it is instructions only. Applying the guidance assumes a Perl runtime and, for some sections, CPAN modules such as DBI, HTML::Entities, URI::Escape, JSON::MaybeXS, IPC::Run3, File::Temp and Crypt::URandom, plus perlcritic for the policy checks.

Perl Security Patterns

Comprehensive security guidelines for Perl applications covering input validation, injection prevention, and secure coding practices.

When to Activate

Handling user input in Perl applications
Building Perl web applications (CGI, Mojolicious, Dancer2, Catalyst)
Reviewing Perl code for security vulnerabilities
Performing file operations with user-supplied paths
Executing system commands from Perl
Writing DBI database queries

How It Works

Start with taint-aware input boundaries, then move outward: validate and untaint inputs, keep filesystem and process execution constrained, and use parameterized DBI queries everywhere. The examples below show the safe defaults this skill expects you to apply before shipping Perl code that touches user input, the shell, or the network.

Taint Mode

Perl's taint mode (-T) tracks data from external sources and prevents it from being used in unsafe operations without explicit validation.

Enabling Taint Mode

perl

#!/usr/bin/perl -Tuse v5.36;
# Tainted: anything from outside the programmy $input    = $ARGV[0];        # Taintedmy $env_path = $ENV{PATH};      # Taintedmy $form     = <STDIN>;         # Taintedmy $query    = $ENV{QUERY_STRING}; # Tainted
# Sanitize PATH early (required in taint mode)$ENV{PATH} = '/usr/local/bin:/usr/bin:/bin';delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};

#!/usr/bin/perl -Tuse v5.36;
# Tainted: anything from outside the programmy $input    = $ARGV[0];        # Taintedmy $env_path = $ENV{PATH};      # Taintedmy $form     = <STDIN>;         # Taintedmy $query    = $ENV{QUERY_STRING}; # Tainted
# Sanitize PATH early (required in taint mode)$ENV{PATH} = '/usr/local/bin:/usr/bin:/bin';delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};

Untainting Pattern

perl

use v5.36;
# Good: Validate and untaint with a specific regexsub untaint_username($input) {    if ($input =~ /^([a-zA-Z0-9_]{3,30})$/) {        return $1;  # $1 is untainted    }    die "Invalid username: must be 3-30 alphanumeric characters\n";}
# Good: Validate and untaint a file pathsub untaint_filename($input) {    if ($input =~ m{^([a-zA-Z0-9._-]+)$}) {        return $1;    }    die "Invalid filename: contains unsafe characters\n";}
# Bad: Overly permissive untainting (defeats the purpose)sub bad_untaint($input) {    $input =~ /^(.*)$/s;    return $1;  # Accepts ANYTHING — pointless}

use v5.36;
# Good: Validate and untaint with a specific regexsub untaint_username($input) {    if ($input =~ /^([a-zA-Z0-9_]{3,30})$/) {        return $1;  # $1 is untainted    }    die "Invalid username: must be 3-30 alphanumeric characters\n";}
# Good: Validate and untaint a file pathsub untaint_filename($input) {    if ($input =~ m{^([a-zA-Z0-9._-]+)$}) {        return $1;    }    die "Invalid filename: contains unsafe characters\n";}
# Bad: Overly permissive untainting (defeats the purpose)sub bad_untaint($input) {    $input =~ /^(.*)$/s;    return $1;  # Accepts ANYTHING — pointless}

Input Validation

Allowlist Over Blocklist

perl

use v5.36;
# Good: Allowlist — define exactly what's permittedsub validate_sort_field($field) {    my %allowed = map { $_ => 1 } qw(name email created_at updated_at);    die "Invalid sort field: $field\n" unless $allowed{$field};    return $field;}
# Good: Validate with specific patternssub validate_email($email) {    if ($email =~ /^([a-zA-Z0-9._%+-]+\@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,})$/) {        return $1;    }    die "Invalid email address\n";}
sub validate_integer($input) {    if ($input =~ /^(-?\d{1,10})$/) {        return $1 + 0;  # Coerce to number    }    die "Invalid integer\n";}
# Bad: Blocklist — always incompletesub bad_validate($input) {    die "Invalid" if $input =~ /[<>"';&|]/;  # Misses encoded attacks    return $input;}

use v5.36;
# Good: Allowlist — define exactly what's permittedsub validate_sort_field($field) {    my %allowed = map { $_ => 1 } qw(name email created_at updated_at);    die "Invalid sort field: $field\n" unless $allowed{$field};    return $field;}
# Good: Validate with specific patternssub validate_email($email) {    if ($email =~ /^([a-zA-Z0-9._%+-]+\@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,})$/) {        return $1;    }    die "Invalid email address\n";}
sub validate_integer($input) {    if ($input =~ /^(-?\d{1,10})$/) {        return $1 + 0;  # Coerce to number    }    die "Invalid integer\n";}
# Bad: Blocklist — always incompletesub bad_validate($input) {    die "Invalid" if $input =~ /[<>"';&|]/;  # Misses encoded attacks    return $input;}

Length Constraints

perl

use v5.36;
sub validate_comment($text) {    die "Comment is required\n"        unless length($text) > 0;    die "Comment exceeds 10000 chars\n" if length($text) > 10_000;    return $text;}

use v5.36;
sub validate_comment($text) {    die "Comment is required\n"        unless length($text) > 0;    die "Comment exceeds 10000 chars\n" if length($text) > 10_000;    return $text;}

Safe Regular Expressions

ReDoS Prevention

Catastrophic backtracking occurs with nested quantifiers on overlapping patterns.

perl

use v5.36;
# Bad: Vulnerable to ReDoS (exponential backtracking)my $bad_re = qr/^(a+)+$/;           # Nested quantifiersmy $bad_re2 = qr/^([a-zA-Z]+)*$/;   # Nested quantifiers on classmy $bad_re3 = qr/^(.*?,){10,}$/;    # Repeated greedy/lazy combo
# Good: Rewrite without nestingmy $good_re = qr/^a+$/;             # Single quantifiermy $good_re2 = qr/^[a-zA-Z]+$/;     # Single quantifier on class
# Good: Use possessive quantifiers or atomic groups to prevent backtrackingmy $safe_re = qr/^[a-zA-Z]++$/;             # Possessive (5.10+)my $safe_re2 = qr/^(?>a+)$/;                # Atomic group
# Good: Enforce timeout on untrusted patternsuse POSIX qw(alarm);sub safe_match($string, $pattern, $timeout = 2) {    my $matched;    eval {        local $SIG{ALRM} = sub { die "Regex timeout\n" };        alarm($timeout);        $matched = $string =~ $pattern;        alarm(0);    };    alarm(0);    die $@ if $@;    return $matched;}

use v5.36;
# Bad: Vulnerable to ReDoS (exponential backtracking)my $bad_re = qr/^(a+)+$/;           # Nested quantifiersmy $bad_re2 = qr/^([a-zA-Z]+)*$/;   # Nested quantifiers on classmy $bad_re3 = qr/^(.*?,){10,}$/;    # Repeated greedy/lazy combo
# Good: Rewrite without nestingmy $good_re = qr/^a+$/;             # Single quantifiermy $good_re2 = qr/^[a-zA-Z]+$/;     # Single quantifier on class
# Good: Use possessive quantifiers or atomic groups to prevent backtrackingmy $safe_re = qr/^[a-zA-Z]++$/;             # Possessive (5.10+)my $safe_re2 = qr/^(?>a+)$/;                # Atomic group
# Good: Enforce timeout on untrusted patternsuse POSIX qw(alarm);sub safe_match($string, $pattern, $timeout = 2) {    my $matched;    eval {        local $SIG{ALRM} = sub { die "Regex timeout\n" };        alarm($timeout);        $matched = $string =~ $pattern;        alarm(0);    };    alarm(0);    die $@ if $@;    return $matched;}

Safe File Operations

Three-Argument Open

perl

use v5.36;
# Good: Three-arg open, lexical filehandle, check returnsub read_file($path) {    open my $fh, '<:encoding(UTF-8)', $path        or die "Cannot open '$path': $!\n";    local $/;    my $content = <$fh>;    close $fh;    return $content;}
# Bad: Two-arg open with user data (command injection)sub bad_read($path) {    open my $fh, $path;        # If $path = "|rm -rf /", runs command!    open my $fh, "< $path";   # Shell metacharacter injection}

use v5.36;
# Good: Three-arg open, lexical filehandle, check returnsub read_file($path) {    open my $fh, '<:encoding(UTF-8)', $path        or die "Cannot open '$path': $!\n";    local $/;    my $content = <$fh>;    close $fh;    return $content;}
# Bad: Two-arg open with user data (command injection)sub bad_read($path) {    open my $fh, $path;        # If $path = "|rm -rf /", runs command!    open my $fh, "< $path";   # Shell metacharacter injection}

TOCTOU Prevention and Path Traversal

perl

use v5.36;use Fcntl qw(:DEFAULT :flock);use File::Spec;use Cwd qw(realpath);
# Atomic file creationsub create_file_safe($path) {    sysopen(my $fh, $path, O_WRONLY | O_CREAT | O_EXCL, 0600)        or die "Cannot create '$path': $!\n";    return $fh;}
# Validate path stays within allowed directorysub safe_path($base_dir, $user_path) {    my $real = realpath(File::Spec->catfile($base_dir, $user_path))        // die "Path does not exist\n";    my $base_real = realpath($base_dir)        // die "Base dir does not exist\n";    die "Path traversal blocked\n" unless $real =~ /^\Q$base_real\E(?:\/|\z)/;    return $real;}

use v5.36;use Fcntl qw(:DEFAULT :flock);use File::Spec;use Cwd qw(realpath);
# Atomic file creationsub create_file_safe($path) {    sysopen(my $fh, $path, O_WRONLY | O_CREAT | O_EXCL, 0600)        or die "Cannot create '$path': $!\n";    return $fh;}
# Validate path stays within allowed directorysub safe_path($base_dir, $user_path) {    my $real = realpath(File::Spec->catfile($base_dir, $user_path))        // die "Path does not exist\n";    my $base_real = realpath($base_dir)        // die "Base dir does not exist\n";    die "Path traversal blocked\n" unless $real =~ /^\Q$base_real\E(?:\/|\z)/;    return $real;}

Use File::Temp for temporary files (tempfile(UNLINK => 1)) and flock(LOCK_EX) to prevent race conditions.

Safe Process Execution

List-Form system and exec

perl

use v5.36;
# Good: List form — no shell interpolationsub run_command(@cmd) {    system(@cmd) == 0        or die "Command failed: @cmd\n";}
run_command('grep', '-r', $user_pattern, '/var/log/app/');
# Good: Capture output safely with IPC::Run3use IPC::Run3;sub capture_output(@cmd) {    my ($stdout, $stderr);    run3(\@cmd, \undef, \$stdout, \$stderr);    if ($?) {        die "Command failed (exit $?): $stderr\n";    }    return $stdout;}
# Bad: String form — shell injection!sub bad_search($pattern) {    system("grep -r '$pattern' /var/log/app/");  # If $pattern = "'; rm -rf / #"}
# Bad: Backticks with interpolationmy $output = `ls $user_dir`;   # Shell injection risk

use v5.36;
# Good: List form — no shell interpolationsub run_command(@cmd) {    system(@cmd) == 0        or die "Command failed: @cmd\n";}
run_command('grep', '-r', $user_pattern, '/var/log/app/');
# Good: Capture output safely with IPC::Run3use IPC::Run3;sub capture_output(@cmd) {    my ($stdout, $stderr);    run3(\@cmd, \undef, \$stdout, \$stderr);    if ($?) {        die "Command failed (exit $?): $stderr\n";    }    return $stdout;}
# Bad: String form — shell injection!sub bad_search($pattern) {    system("grep -r '$pattern' /var/log/app/");  # If $pattern = "'; rm -rf / #"}
# Bad: Backticks with interpolationmy $output = `ls $user_dir`;   # Shell injection risk

Also use Capture::Tiny for capturing stdout/stderr from external commands safely.

SQL Injection Prevention

DBI Placeholders

perl

use v5.36;use DBI;
my $dbh = DBI->connect($dsn, $user, $pass, {    RaiseError => 1,    PrintError => 0,    AutoCommit => 1,});
# Good: Parameterized queries — always use placeholderssub find_user($dbh, $email) {    my $sth = $dbh->prepare('SELECT * FROM users WHERE email = ?');    $sth->execute($email);    return $sth->fetchrow_hashref;}
sub search_users($dbh, $name, $status) {    my $sth = $dbh->prepare(        'SELECT * FROM users WHERE name LIKE ? AND status = ? ORDER BY name'    );    $sth->execute("%$name%", $status);    return $sth->fetchall_arrayref({});}
# Bad: String interpolation in SQL (SQLi vulnerability!)sub bad_find($dbh, $email) {    my $sth = $dbh->prepare("SELECT * FROM users WHERE email = '$email'");    # If $email = "' OR 1=1 --", returns all users    $sth->execute;    return $sth->fetchrow_hashref;}

use v5.36;use DBI;
my $dbh = DBI->connect($dsn, $user, $pass, {    RaiseError => 1,    PrintError => 0,    AutoCommit => 1,});
# Good: Parameterized queries — always use placeholderssub find_user($dbh, $email) {    my $sth = $dbh->prepare('SELECT * FROM users WHERE email = ?');    $sth->execute($email);    return $sth->fetchrow_hashref;}
sub search_users($dbh, $name, $status) {    my $sth = $dbh->prepare(        'SELECT * FROM users WHERE name LIKE ? AND status = ? ORDER BY name'    );    $sth->execute("%$name%", $status);    return $sth->fetchall_arrayref({});}
# Bad: String interpolation in SQL (SQLi vulnerability!)sub bad_find($dbh, $email) {    my $sth = $dbh->prepare("SELECT * FROM users WHERE email = '$email'");    # If $email = "' OR 1=1 --", returns all users    $sth->execute;    return $sth->fetchrow_hashref;}

Dynamic Column Allowlists

perl

use v5.36;
# Good: Validate column names against an allowlistsub order_by($dbh, $column, $direction) {    my %allowed_cols = map { $_ => 1 } qw(name email created_at);    my %allowed_dirs = map { $_ => 1 } qw(ASC DESC);
    die "Invalid column: $column\n"    unless $allowed_cols{$column};    die "Invalid direction: $direction\n" unless $allowed_dirs{uc $direction};
    my $sth = $dbh->prepare("SELECT * FROM users ORDER BY $column $direction");    $sth->execute;    return $sth->fetchall_arrayref({});}
# Bad: Directly interpolating user-chosen columnsub bad_order($dbh, $column) {    $dbh->prepare("SELECT * FROM users ORDER BY $column");  # SQLi!}

use v5.36;
# Good: Validate column names against an allowlistsub order_by($dbh, $column, $direction) {    my %allowed_cols = map { $_ => 1 } qw(name email created_at);    my %allowed_dirs = map { $_ => 1 } qw(ASC DESC);
    die "Invalid column: $column\n"    unless $allowed_cols{$column};    die "Invalid direction: $direction\n" unless $allowed_dirs{uc $direction};
    my $sth = $dbh->prepare("SELECT * FROM users ORDER BY $column $direction");    $sth->execute;    return $sth->fetchall_arrayref({});}
# Bad: Directly interpolating user-chosen columnsub bad_order($dbh, $column) {    $dbh->prepare("SELECT * FROM users ORDER BY $column");  # SQLi!}

DBIx::Class (ORM Safety)

perl

use v5.36;
# DBIx::Class generates safe parameterized queriesmy @users = $schema->resultset('User')->search({    status => 'active',    email  => { -like => '%@example.com' },}, {    order_by => { -asc => 'name' },    rows     => 50,});

use v5.36;
# DBIx::Class generates safe parameterized queriesmy @users = $schema->resultset('User')->search({    status => 'active',    email  => { -like => '%@example.com' },}, {    order_by => { -asc => 'name' },    rows     => 50,});

Web Security

XSS Prevention

perl

use v5.36;use HTML::Entities qw(encode_entities);use URI::Escape qw(uri_escape_utf8);
# Good: Encode output for HTML contextsub safe_html($user_input) {    return encode_entities($user_input);}
# Good: Encode for URL contextsub safe_url_param($value) {    return uri_escape_utf8($value);}
# Good: Encode for JSON contextuse JSON::MaybeXS qw(encode_json);sub safe_json($data) {    return encode_json($data);  # Handles escaping}
# Template auto-escaping (Mojolicious)# <%= $user_input %>   — auto-escaped (safe)# <%== $raw_html %>    — raw output (dangerous, use only for trusted content)
# Template auto-escaping (Template Toolkit)# [% user_input | html %]  — explicit HTML encoding
# Bad: Raw output in HTMLsub bad_html($input) {    print "<div>$input</div>";  # XSS if $input contains <script>}

use v5.36;use HTML::Entities qw(encode_entities);use URI::Escape qw(uri_escape_utf8);
# Good: Encode output for HTML contextsub safe_html($user_input) {    return encode_entities($user_input);}
# Good: Encode for URL contextsub safe_url_param($value) {    return uri_escape_utf8($value);}
# Good: Encode for JSON contextuse JSON::MaybeXS qw(encode_json);sub safe_json($data) {    return encode_json($data);  # Handles escaping}
# Template auto-escaping (Mojolicious)# <%= $user_input %>   — auto-escaped (safe)# <%== $raw_html %>    — raw output (dangerous, use only for trusted content)
# Template auto-escaping (Template Toolkit)# [% user_input | html %]  — explicit HTML encoding
# Bad: Raw output in HTMLsub bad_html($input) {    print "<div>$input</div>";  # XSS if $input contains <script>}

CSRF Protection

perl

use v5.36;use Crypt::URandom qw(urandom);use MIME::Base64 qw(encode_base64url);
sub generate_csrf_token() {    return encode_base64url(urandom(32));}

use v5.36;use Crypt::URandom qw(urandom);use MIME::Base64 qw(encode_base64url);
sub generate_csrf_token() {    return encode_base64url(urandom(32));}

Use constant-time comparison when verifying tokens. Most web frameworks (Mojolicious, Dancer2, Catalyst) provide built-in CSRF protection — prefer those over hand-rolled solutions.

Session and Header Security

perl

use v5.36;
# Mojolicious session + headers$app->secrets(['long-random-secret-rotated-regularly']);$app->sessions->secure(1);          # HTTPS only$app->sessions->samesite('Lax');
$app->hook(after_dispatch => sub ($c) {    $c->res->headers->header('X-Content-Type-Options' => 'nosniff');    $c->res->headers->header('X-Frame-Options'        => 'DENY');    $c->res->headers->header('Content-Security-Policy' => "default-src 'self'");    $c->res->headers->header('Strict-Transport-Security' => 'max-age=31536000; includeSubDomains');});

use v5.36;
# Mojolicious session + headers$app->secrets(['long-random-secret-rotated-regularly']);$app->sessions->secure(1);          # HTTPS only$app->sessions->samesite('Lax');
$app->hook(after_dispatch => sub ($c) {    $c->res->headers->header('X-Content-Type-Options' => 'nosniff');    $c->res->headers->header('X-Frame-Options'        => 'DENY');    $c->res->headers->header('Content-Security-Policy' => "default-src 'self'");    $c->res->headers->header('Strict-Transport-Security' => 'max-age=31536000; includeSubDomains');});

Output Encoding

Always encode output for its context: HTML::Entities::encode_entities() for HTML, URI::Escape::uri_escape_utf8() for URLs, JSON::MaybeXS::encode_json() for JSON.

CPAN Module Security

Pin versions in cpanfile: requires 'DBI', '== 1.643';
Prefer maintained modules: Check MetaCPAN for recent releases
Minimize dependencies: Each dependency is an attack surface

Security Tooling

perlcritic Security Policies

ini

# .perlcriticrc — security-focused configurationseverity = 3theme = security + core
# Require three-arg open[InputOutput::RequireThreeArgOpen]severity = 5
# Require checked system calls[InputOutput::RequireCheckedSyscalls]functions = :builtinsseverity = 4
# Prohibit string eval[BuiltinFunctions::ProhibitStringyEval]severity = 5
# Prohibit backtick operators[InputOutput::ProhibitBacktickOperators]severity = 4
# Require taint checking in CGI[Modules::RequireTaintChecking]severity = 5
# Prohibit two-arg open[InputOutput::ProhibitTwoArgOpen]severity = 5
# Prohibit bare-word filehandles[InputOutput::ProhibitBarewordFileHandles]severity = 5

# .perlcriticrc — security-focused configurationseverity = 3theme = security + core
# Require three-arg open[InputOutput::RequireThreeArgOpen]severity = 5
# Require checked system calls[InputOutput::RequireCheckedSyscalls]functions = :builtinsseverity = 4
# Prohibit string eval[BuiltinFunctions::ProhibitStringyEval]severity = 5
# Prohibit backtick operators[InputOutput::ProhibitBacktickOperators]severity = 4
# Require taint checking in CGI[Modules::RequireTaintChecking]severity = 5
# Prohibit two-arg open[InputOutput::ProhibitTwoArgOpen]severity = 5
# Prohibit bare-word filehandles[InputOutput::ProhibitBarewordFileHandles]severity = 5

Running perlcritic

bash

# Check a fileperlcritic --severity 3 --theme security lib/MyApp/Handler.pm
# Check entire projectperlcritic --severity 3 --theme security lib/
# CI integrationperlcritic --severity 4 --theme security --quiet lib/ || exit 1

# Check a fileperlcritic --severity 3 --theme security lib/MyApp/Handler.pm
# Check entire projectperlcritic --severity 3 --theme security lib/
# CI integrationperlcritic --severity 4 --theme security --quiet lib/ || exit 1

Quick Security Checklist

Check	What to Verify
Taint mode	`-T` flag on CGI/web scripts
Input validation	Allowlist patterns, length limits
File operations	Three-arg open, path traversal checks
Process execution	List-form system, no shell interpolation
SQL queries	DBI placeholders, never interpolate
HTML output	`encode_entities()`, template auto-escape
CSRF tokens	Generated, verified on state-changing requests
Session config	Secure, HttpOnly, SameSite cookies
HTTP headers	CSP, X-Frame-Options, HSTS
Dependencies	Pinned versions, audited modules
Regex safety	No nested quantifiers, anchored patterns
Error messages	No stack traces or paths leaked to users

Anti-Patterns

perl

# 1. Two-arg open with user data (command injection)open my $fh, $user_input;               # CRITICAL vulnerability
# 2. String-form system (shell injection)system("convert $user_file output.png"); # CRITICAL vulnerability
# 3. SQL string interpolation$dbh->do("DELETE FROM users WHERE id = $id");  # SQLi
# 4. eval with user input (code injection)eval $user_code;                         # Remote code execution
# 5. Trusting $ENV without sanitizingmy $path = $ENV{UPLOAD_DIR};             # Could be manipulatedsystem("ls $path");                      # Double vulnerability
# 6. Disabling taint without validation($input) = $input =~ /(.*)/s;           # Lazy untaint — defeats purpose
# 7. Raw user data in HTMLprint "<div>Welcome, $username!</div>";  # XSS
# 8. Unvalidated redirectsprint $cgi->redirect($user_url);         # Open redirect

# 1. Two-arg open with user data (command injection)open my $fh, $user_input;               # CRITICAL vulnerability
# 2. String-form system (shell injection)system("convert $user_file output.png"); # CRITICAL vulnerability
# 3. SQL string interpolation$dbh->do("DELETE FROM users WHERE id = $id");  # SQLi
# 4. eval with user input (code injection)eval $user_code;                         # Remote code execution
# 5. Trusting $ENV without sanitizingmy $path = $ENV{UPLOAD_DIR};             # Could be manipulatedsystem("ls $path");                      # Double vulnerability
# 6. Disabling taint without validation($input) = $input =~ /(.*)/s;           # Lazy untaint — defeats purpose
# 7. Raw user data in HTMLprint "<div>Welcome, $username!</div>";  # XSS
# 8. Unvalidated redirectsprint $cgi->redirect($user_url);         # Open redirect

Remember: Perl's flexibility is powerful but requires discipline. Use taint mode for web-facing code, validate all input with allowlists, use DBI placeholders for every query, and encode all output for its context. Defense in depth — never rely on a single layer.

Source and attribution

Source:affaan-m/ECCinskills/perl-securityat commitef648e0

License: No license

Content belongs to its original authors. SourceWeft indexes it from a public repository.

Report or request removal

Perl Security

Perl Security Patterns

When to Activate

How It Works

Taint Mode

Enabling Taint Mode

Untainting Pattern

Input Validation

Allowlist Over Blocklist

Length Constraints

Safe Regular Expressions

ReDoS Prevention

Safe File Operations

Three-Argument Open

TOCTOU Prevention and Path Traversal

Safe Process Execution

List-Form system and exec

SQL Injection Prevention

DBI Placeholders

Dynamic Column Allowlists

DBIx::Class (ORM Safety)

Web Security

XSS Prevention

CSRF Protection

Session and Header Security

Output Encoding

CPAN Module Security

Security Tooling

perlcritic Security Policies

Running perlcritic

Quick Security Checklist

Anti-Patterns

Source and attribution

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