This script demonstrates a use of HTML::Parser to determine if a web page contains a script tag, or if an html tag contains an event attribute.

I realize that this script takes what I'd call an exclusive method of approval (does the page contain something on a banned list?) rather than an inclusive method (does the page contain something not on an approved list) and is therefore more vulnerable to trickery or changes/ additions to what browsers think is an acceptable javascript event.
I hope this script is useful, but you've been warned. As always, your comments, criticisms and baseless accusations are welcome.

Update Removed the event list and added dws' suggestion for a regex to search for /on\w+/
Added belg4mit's suggestions :

  1. elements passed to check_attrs will get URI decoded
  2. added mocha & data as forbidden protocols. If anyone has further suggestions, or a list of pseudo-protocols that should be included, I'd love to see it.
  3. added check for javascript entities
script doesn't die on first error found anymore. Cleaned up output a bit. 
#! perl -w
use HTML::Parser;
use LWP::Simple;
use URI::Escape;
use strict;

my $fn = shift;
$fn || die "supply a url to parse\n";    
my $f = get ($fn) || die "unable to get $fn\n";    

HTML::Parser->new(
    default_h => [\&check_attrs, 'text, tagname,  attr'],             
+  
)->parse($f ) || die $!;


sub check_attrs {
    my @forbiddenprotos= qw(javascript mocha data);
    
    my $line = shift;
    my $tagname = shift;
    return unless $tagname;
    $tagname = uri_unescape($tagname);
    print "found script tag.\n\t$line\n" if $tagname eq "script";
    my $attr = shift;
    my $attrs = uri_unescape(join " ", keys %$attr);    
    my $attrvals = uri_unescape(join " ", values %$attr);
    print "events $1 found.\n\t$line\n" if $attrs=~/\b(on\w+)/;
    foreach (@forbiddenprotos) {
        print "$_ protocol found.\n\t$line\n" if $attrvals=~/\b$_:/;
    }
    print "javascript entity found.\n\t$line\n" if $attrvals=~/\&\{/;
}

[download]

In reply to Am I javascript or not? by boo_radley

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