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.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.