GHSA-gwpm-pm6x-h7rj ZendFramework Cross-site Scripting vector in `Zend_Filter_StripTags`
An XSS vulnerability in Zend_Filter_StripTags allows attackers to inject scripts via whitespace in attributes when using attribute whitelisting.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is GHSA-gwpm-pm6x-h7rj?
GHSA-gwpm-pm6x-h7rj is a cross-site scripting vulnerability in zendframework/zendframework1, published on 7 Jun 2024. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Zend_Filter_StripTags is a filtering class analogous to PHP's strip_tags() function. In addition to stripping HTML tags and selectively keeping those provided in a whitelist, it also provides the ability to whitelist specific attributes to retain per whitelisted tag.
The reporter discovered that attributes that contained whitespace, and in paricular, line breaks, surrounding the attribute assignment operator would not be stripped, regardless of whether or not they were whitelisted. As examples of input affected:
<!-- newlines before and/or after assignment: -->
<a href="http://framework.zend.com/issues" onclick
=
"alert('Broken'); return false;">Issues</a>
When passed to the following code:
$filter = new Zend_Filter_StripTags(array('a' => array('href')));
$value = $filter->($html);
then the "onclick" attribute would remain, even though it was not specified in the tag's whitelist. This could open potential cross-site scripting attack (XSS) vectors.
Recommendations
If you were using Zend_Filter_StripTags and utlizing the attribute whitelisting functionality, you should immediately upgrade to Zend Framework 1.7.6 or above; regardless, it is always best to run the most current version of the framework.
Also, if relying on Zend_Filter_StripTags to prevent XSS, the only way to reliably do so is to strip all tags, and never to whitelist. If you are whitelisting, you should consider finding a reliable XSS filter through which to run your output; we recommend HTML Purifier.
Which versions are affected by GHSA-gwpm-pm6x-h7rj?
2 open source packages ship an affected version, including zendframework/zendframework1.
| Package | Affected | Fixed in |
|---|---|---|
zendframework/zendframework1 Packagist | From 1.7.0 | 1.7.6 |
zendframework/zendframework1 Packagist | From 1.7.0 | 1.7.6 |
How do I fix GHSA-gwpm-pm6x-h7rj?
Upgrade zendframework/zendframework1 to 1.7.6 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is GHSA-gwpm-pm6x-h7rj being exploited?
There is no known exploitation of GHSA-gwpm-pm6x-h7rj in the wild and no public exploit code.