MailerPress <= 1.5.0 - Missing Authorization to Unauthenticated Arbitrary Modification via REST API Endpoint

The MailPress plugin for WordPress is vulnerable to unauthorized access in versions up to, and including, 1.5.0 via the campaign revision-restore REST endpoint (POST /wp-json/mailpress/v1/campaign/<id>/restore-revision/<revision_id>). The route in the vulnerable range was registered without a permissionCallback, allowing the restoreRevision() handler to run for unauthenticated requests and overwrite a campaign's content_html with any prior revision. This makes it possible for unauthenticated attackers to modify campaign content by restoring an arbitrary revision.