Dnn.Platform uses an insecure encryption key. The vulnerability exists as it does not actually use an encrypted key as its key.
packetstormsecurity.com/files/157080/DotNetNuke-Cookie-Deserialization-Remote-Code-Execution.html
github.com/dnnsoftware/Dnn.Platform/commit/99bf22270b28c5124ae5ada6c9cf00b2901efb3a
github.com/dnnsoftware/Dnn.Platform/releases
github.com/dnnsoftware/Dnn.Platform/releases/tag/v9.2.2
www.dnnsoftware.com/community/security/security-center