In affected versions of Progress® Telerik® UI for ASP.NET MVC `2012.2.710` through `2026.3.811`, ClassFactory updates a shared class dictionary without exclusive write protection and emits non-collectible dynamic assemblies that remain loaded for the AppDomain's lifetime. The dictionary lookup and insertion are not atomic, and case variations in aggregate descriptors can produce distinct retained types even though member resolution is case-insensitive. An unauthenticated remote attacker can exploit this if the application exposes an aggregation endpoint that is reachable without authentication, by submitting concurrent or repeated crafted requests. These requests may corrupt dictionary state