functions/html_to_text.php in the Chat module before 1.5.2 for activeCollab allows remote authenticated users to execute arbitrary PHP code via the message[message_text] parameter to chat/add_messag, which is not properly handled when executing the preg_replace function with the eval switch.
https://exchange.xforce.ibmcloud.com/vulnerabilities/75741
http://www.securityfocus.com/bid/53624
http://www.activecollab.com/downloads/category/4/package/62/releases