ActivityPub < 1.0.0 is vulnerable to Subscriber+ Arbitrary Post Title Disclosure vulnerability

The ActivityPub plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to, and including, 0.17.0 due to missing validation on a user controlled key. This can allow authenticated attackers, with subscriber-level permissions and above, to expose potentially sensitive post titles (e.g., draft and private post titles).