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GHSA-gwpm-pm6x-h7rj
No affected components available
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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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