An open redirect vulnerability exposes OpenCATS to template injection due to improper validation of user-supplied GET parameters.

Improper neutralization of input during web page generation allows an authenticated attacker with access to a restricted account to submit malicious Javascript as the description for a calendar event, which would then be executed in other users' browsers if they browse to that event. This could result in stealing session tokens from users with higher permission levels or forcing users to make actions without their knowledge.

Cross-site request forgery is facilitated by OpenCATS failure to require CSRF tokens in POST requests. An attacker can exploit this issue by creating a dummy page that executes Javascript in an authenticated user's session when visited.

Improper neutralization of input during web page generation allows an unauthenticated attacker to submit malicious Javascript as the answer to a questionnaire which would then be executed when an authenticated user reviews the candidate's submission. This could be used to steal other users’ cookies and force users to make actions without their knowledge.

OpenCATS through 0.9.6 allows remote attackers to execute arbitrary code by uploading an executable file via lib/FileUtility.php.