Como corregir vulnerabilidad en Google Website Optimizer

El día de hoy Google ha enviado un mail indicando que todos los tests que se estén llevando a cabo en Website Optimizer deben ser actualizados en cuanto al código por una vulnerabilidad de tipo XSS. Es algo sencillo de hacer simplemente en el código hay que buscar la linea:

return c.substring(i+n.length+1,j<0?c.length:j)

Y cambiarla por:

return escape(c.substring(i+n.length+1,j<0?c.length:j))

De acuerdo a la información de Google, este cambio se debe hacer en todo test que se haya iniciado antes del 3 de diciembre 2010.

Si no se desea tocar el código se puede generar un nuevo test, que ya automaticamente tienen corregido el problema.

Dear Website Optimiser user,

We are writing to inform you of a potential security issue with Website Optimiser. By exploiting a vulnerability in the Website Optimiser Control Script, an attacker might be able to execute malicious code on your site using a Cross-Site Scripting (XSS) attack. This attack can only take place if a website or browser has already been compromised by a separate attack. While the immediate probability of this attack is low, we urge you to take action to protect your site.

We have fixed the bug, and all new experiments are not susceptible. However, any experiments you are currently running need to be updated to fix the bug on your site. Additionally, if you have any Website Optimiser scripts from paused or stopped experiments created before 3 December 2010, you will need to remove or update that code as well.

There are two ways to update your code. You can either stop current experiments, remove the old scripts and create a new experiment, or you can update the code on your site directly. We strongly recommend creating a new experiment as it is the simpler method.

Creating a New Experiment

1. Stop any currently running Website Optimiser experiments
2. Remove all the Website Optimiser scripts from your site
3. Create a new experiment as normal. New experiments are not vulnerable.

Updating the Website Optimizer Control Script Directly

1. Locate the Control Script on your site. It looks like this:

A/B Test Control Script
<!-- Google Website Optimiser Control Script -->
<script>
function utmx_section(){}function utmx(){}
(function(){var k='XXXXXXXXXX',d=document,l=d.location,c=d.cookie;function f(n){
if(c){var i=c.indexOf(n+'=');if(i>-1){var j=c.indexOf(';',i);return c.substring(i+n.
length+1,j<0?c.length:j)}}}var x=f('__utmx'),xx=f('__utmxx'),h=l.hash;
d.write('<sc'+'ript src="'+
'http'+(l.protocol=='https:'?'s://ssl':'://www')+'.google-analytics.com'
+'/siteopt.js?v=1&utmxkey='+k+'&utmx='+(x?x:'')+'&utmxx='+(xx?xx:'')+'&utmxtime='
+new Date().valueOf()+(h?'&utmxhash='+escape(h.substr(1)):'')+
'" type="text/javascript" charset="utf-8"></sc'+'ript>')})();
</script><script>utmx("url",'A/B');</script>
<!-- End of Google Website Optimizer Control Script -->

Multivariate Test Control Script
<!-- Google Website Optimizer Control Script -->
<script>
function utmx_section(){}function utmx(){}
(function(){var k='XXXXXXXXXX',d=document,l=d.location,c=d.cookie;function f(n){
if(c){var i=c.indexOf(n+'=');if(i>-1){var j=c.indexOf(';',i);return c.substring(i+n.
length+1,j<0?c.length:j)}}}var x=f('__utmx'),xx=f('__utmxx'),h=l.hash;
d.write('<sc'+'ript src="'+
'http'+(l.protocol=='https:'?'s://ssl':'://www')+'.google-analytics.com'
+'/siteopt.js?v=1&utmxkey='+k+'&utmx='+(x?x:'')+'&utmxx='+(xx?xx:'')+'&utmxtime='
+new Date().valueOf()+(h?'&utmxhash='+escape(h.substr(1)):'')+
'" type="text/javascript" charset="utf-8"></sc'+'ript>')})();
</script>
<-- End of Google Website Optimizer Control Script -->

1. Locate the following in the Control Script: return c.substring(...
2. Modify the following line as shown:
   BEFORE: return c.substring(i+n.length+1,j<0?c.length:j)
   FIXED: return escape(c.substring(i+n.length+1,j<0?c.length:j))
   Make sure to include the final closing brackets “)”

Fixed A/B Control Script
<!-- Google Website Optimizer Control Script -->
<script>
function utmx_section(){}function utmx(){} (function(){var k='XXXXXXXXXX',d=document,l=d.location,c=d.cookie;function f(n){ if(c){var i=c.indexOf(n+'=');if(i>-1){var j=c.indexOf(';',i);
return escape(c.substring(i+n.length+1,j<0?c.length:j))}}}
var x=f('__utmx'),xx=f('__utmxx'),h=l.hash; d.write('<sc'+'ript src="'+
'http'+(l.protocol=='https:'?'s://ssl':'://www')+'.google-analytics.com'
+'/siteopt.js?v=1&utmxkey='+k+'&utmx='+(x?x:'')+'&utmxx='+(xx?xx:'')+'&utmxtime='
+new Date().valueOf()+(h?'&utmxhash='+escape(h.substr(1)):'')+
'" type="text/javascript" charset="utf-8"></sc'+'ript>')})();
</script><script>utmx("url",'A/B');
</script>
<-- End of Google Website Optimizer Control Script -->

Fixed Multivariate Control Script
<!-- Google Website Optimizer Control Script -->
<script>
function utmx_section(){}function utmx(){}
(function(){var k='XXXXXXXXXX',d=document,l=d.location,c=d.cookie;function f(n){
if(c){var i=c.indexOf(n+'=');if(i>-1){var j=c.indexOf(';',i);
return escape(c.substring(i+n.length+1,j<0?c.length:j))}}}
var x=f('__utmx'),xx=f('__utmxx'),h=l.hash; d.write('<sc'+'ript src="'+
'http'+(l.protocol=='https:'?'s://ssl':'://www')+'.google-analytics.com'
+'/siteopt.js?v=1&utmxkey='+k+'&utmx='+(x?x:'')+'&utmxx='+(xx?xx:'')+'&utmxtime='
+new Date().valueOf()+(h?'&utmxhash='+escape(h.substr(1)):'')+
'" type="text/javascript" charset="utf-8"></sc'+'ript>')})();
</script>
<-- End of Google Website Optimizer Control Script -->

Note that the k=XXXXXXXXX line in the above Control Script examples is a placeholder.

Your experiment will continue as normal after you’ve made this update. There’s no need to pause or restart the experiment.

We’re committed to keeping Website Optimiser secure, and we’re deeply sorry for this issue. We will continue to work hard to prevent future vulnerabilities.

Yours sincerely,
Trevor
Google Website Optimiser Team

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