YesWiki is a wiki system written in PHP. In versions up to and including 4.4.5, it is possible for any authenticated user, through the use of the filemanager to delete any file owned by the user running the FastCGI Process Manager (FPM) on the host without any limitation on the filesystem's scope. This vulnerability allows any authenticated user to arbitrarily remove content from the Wiki resulting in partial loss of data and defacement/deterioration of the website.

In the context of a container installation of YesWiki without any modification, the yeswiki files (for example .php) are not owned by the same user (root) as the one running the FPM process (www-data). However in a standard installation, www-data may also be the owner of the PHP files, allowing a malicious user to completely cut the access to the wiki by deleting all important PHP files (like index.php or core files of YesWiki). Version 4.5.0 contains a patch for this issue.