Cross-site scripting vulnerability in Edit screen of Content Data of Movable Type (Movable Type 7 r.4903 and earlier (Movable Type 7 Series) and Movable Type Advanced 7 r.4903 and earlier (Movable Type Advanced 7 Series)) allows remote attackers to inject arbitrary script or HTML via unspecified vectors.
https://movabletype.org/news/2021/08/mt-780-681-released.html