ZF2010-03: Potential XSS vector in Zend_Filter_StripTags when comments allowed
Zend_Filter_StripTags contained an optional setting to allow
whitelisting HTML comments in filtered text. Microsoft Internet Explorer
and several other browsers allow developers to create conditional
functionality via HTML comments, including execution of script events
and rendering of additional commented markup. By allowing whitelisting
of HTML comments, a malicious user could potentially include XSS
exploits within HTML comments that would then be rendered in the final
The Zend Framework team has determined that since this vulnerability is so trivial to exploit, the functionality to allow whitelisting comments will now be disabled in this and all future releases. Additionally, the regular expression for stripping comments has been bolstered to properly remove comments containing HTML tags, nested comments, and comments ending with whitespace between the "--" and ending delimiter (">").
If you use this filter and were enabling the "allowComments" functionality, be advised that it is now silently ignored. We also recommend such users to upgrade to the latest available Zend Framework release, or one of the following releases, immediately.
The Zend Framework team thanks the following for working with us to help protect its users:
- Pádraic Brady, who made the initial report and who worked with our team to ensure that the appropriate actions were taken
Reporting Potential Security Issues
If you have encountered a potential security vulnerability in Zend Framework, please report it to us at email@example.com. We will work with you to verify the vulnerability and patch it.
When reporting issues, please provide the following information:
- Component(s) affected
- A description indicating how to reproduce the issue
- A summary of the security vulnerability and impact
We request that you contact us via the email address above and give the project contributors a chance to resolve the vulnerability and issue a new release prior to any public exposure; this helps protect Zend Framework users and provides them with a chance to upgrade and/or update in order to protect their applications.
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Zend Framework takes security seriously. If we verify a reported security vulnerability, our policy is:
- We will patch the current release branch, as well as the immediate prior minor release branch.
- After patching the release branches, we will immediately issue new security fix releases for each patched release branch.
- A security advisory will be released on the Zend Framework site detailing the vulnerability, as well as recommendations for end-users to protect themselves. Security advisories will be listed at http://framework.zend.com/security/advisories, as well as via a feed (which is also present in the website head for easy feed discovery)