Deserialization of Untrusted Data in the anti CSRF module in Sitecore through 9.1 allows an authenticated attacker to execute arbitrary code by sending a serialized .NET object in an HTTP POST parameter.
https://thehackernews.com/2025/03/cisa-flags-two-six-year-old-sitecore.html
https://www.synacktiv.com/ressources/advisories/Sitecore_CSRF_deserialize_RCE.pdf