MISP contains an incomplete authorization check in the discussion posting functionality. When a user submits a post to a thread or replies to an existing post, the application only verified whether the target thread was restricted to a single organization (org-only distribution). It did not enforce the full thread access control list, including sharing-group membership and event-level visibility.
As a result, an authenticated user who is outside the relevant sharing group or who does not have visibility on the associated event could:
This constitutes both an information disclosure (reading restricted thread and post content) and an integrity issue (injecting content into a thread the user is not authorized to participate in).
Affected: <2.5.48
The fix replaces the limited org-only distribution check with a call to the thread's full authorization method (checkIfAuthorised), which enforces the complete access control list including sharing groups and event-level visibility. The thread is only read after successful authorization, preventing disclosure of the title and content to unauthorized users. An additional null-check on the post's thread_id was added to prevent referencing posts without a valid thread association.