TikiWiki is a web-based groupware and content management system (CMS), using PHP, ADOdb and Smarty.
TikiWiki lacks a check on uploaded images in the Wiki edit page.
A malicious user could run arbitrary commands on the server by uploading and calling a PHP script.
There is no known workaround at this time.
All TikiWiki users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=www-apps/tikiwiki-1.8.4.1"
Note: Users with the vhosts USE flag set should manually use webapp-config to finalize the update.