The Better Messages – Chat Rooms, Group Chat, Private Messages & AI Chat Bots plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 2.15.33. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with custom-level access and above, to access the full message transcript, thread metadata, and user data of any chat-room thread without authentication. This is only exploitable when the chat room's only_joined_can_read setting retains its default value of '0'.
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/rest-api.php#L418
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/rest-api.php#L2598
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/rest-api.php#L1964
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/rest-api.php#L181
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/functions.php#L3601
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/functions.php#L3582
https://plugins.trac.wordpress.org/browser/bp-better-messages/tags/2.15.33/inc/functions.php#L3533