Serendipity (S9Y) is a popular blogging system.
Serendipity has the trustxss plugin to prevent XSS between users on multiuser setups, but that doesn't catch these issues.
Beside, the media library accepts uploads from any file format, including htm, html and js, which obviously also leads to xss.
If you have a multiuser-blog and don't trust all users, you need to install the trustxss plugin and should
immediately upgrade to 1.3-beta1.
If you're using a single-user blog, you are not affected.
2008-02-01 Vendor contacted
2008-02-01 Vendor fixed svn
2007-02-25 Vendor released 1.3-beta1
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-0124 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.
This vulnerability was discovered by Hanno Boeck of schokokeks.org webhosting. It's licensed under the creative commons attribution license.
Hanno Boeck, 2008-02-26, http://www.hboeck.de