Serendipity bundles the powerful Xinha WYSIWYG editor to provide its functionality to our users.
Xinha ships with several plugins that utilize PHP scripting for special usage, like the ImageManager or ExtendedFileManager. A 0-day security exploit has been reported available as of today that exploits the functionality of these plugins to upload malicious files to your webspace, to execute foreign code.
Since no official patch has been made on the Xinha side, the Serendipity Team has released an updated version where those active Xinha-Plugins are no longer executable.
If you do not wish to apply the patch to the most recent Serendipity version 1.5.5 you can remove those files:
The provided functionality is usually not enabled by default, since Serendipity provides its own media file manager.
Future serendipity releases might re-enable these features, once they are safely patched.
To see if you are infected, please check the directories htmlarea/plugins/ImageManager/demo_images and htmlarea/plugins/ExtendedFileManager/demo_images to see if files have been uploaded there. If so, delete the files and check your webspace for other modified files, as well as change your passwords for FTP and SQL access. Please upgrade as soon as possible.
The release can be found on the Serendipity Download page. All serendipity versions from 1.4 to 1.6 (alpha) are affected. 1.6 alpha users should migrate to a recent SVN head checkout or tomorrow's snapshot.
Thanks a lot to Hauser & Wenz for reporting the issue. Serendipity fully acknowledges responsible full disclosure, non-reported 0-day exploits are helping nobody of true OpenSource spirit.