FreeScout: Conversation Merge Cross-Mailbox Authorization Bypass

FreeScout is a self-hosted help desk and shared mailbox. Prior to 1.8.227, the conversation_merge action records a failed authorization check for the target conversation in response['msg'] and then clears that value inside the source-conversation loop. An authenticated agent can merge a conversation they control into a target conversation in a mailbox they cannot access. The operation injects threads, attachments, and audit records into the unauthorized target and deletes the source conversation, but it does not disclose the target's existing contents. This issue is fixed in version 1.8.227.