YesWiki is a wiki system written in PHP. Prior to version 4.5.4, YesWiki vulnerable to remote code execution. An arbitrary file write can be used to write a file with a PHP extension, which then can be browsed to in order to execute arbitrary code on the server, resulting in a full compromise of the server. This could potentially be performed unwittingly by a user. This issue has been patched in version 4.5.4.

YesWiki Remote Code Execution via Arbitrary PHP File Write and Execution