YesWiki is a wiki system written in PHP. Prior to version 4.5.4, the request to commence a site backup can be performed and downloaded without authentication. The archives are created with a predictable filename, so a malicious user could create and download an archive without being authenticated. This could result in a malicious attacker making numerous requests to create archives and fill up the file system, or by downloading the archive which contains sensitive site information. This issue has been patched in version 4.5.4.