Cross-site scripting vulnerability in Movable Type Movable Type 7 r.5301 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.5301 and earlier (Movable Type Advanced 7 Series), Movable Type 6.8.7 and earlier (Movable Type 6 Series), Movable Type Advanced 6.8.7 and earlier (Movable Type Advanced 6 Series), Movable Type Premium 1.53 and earlier, and Movable Type Premium Advanced 1.53 and earlier allows a remote unauthenticated attacker to inject an arbitrary script.
https://movabletype.org/news/2022/11/mt-796-688-released.html