We have been made aware of several security issues with Geeklog 1.3.5 (earlier versions are probably affected as well). These allow for the injection of malicious javascript code which could be used e.g. to take over the admin's cookie. There is also an issue that allows the injection of MySQL requests from outside, possibly exposing data or even damaging the database (under certain circumstances). Details about these problems will be posted on the Bugtraq list later today.
In order to secure your installations, we have released Geeklog 1.3.5sr1 which addresses these issues. You are strongly encouraged to upgrade to this version as soon as possible.
If your site is running Geeklog 1.3.5, you could also download this file which contains just the affected files. After uploading them, your installation will be secure. Please note that this may overwrite customisations you may have made to the affected files.