Symptoms

Server Error - A potentially dangerous request.form value was detected from the client….
I am getting the attached error message in several section of the workspace, for example, creating a role, retry in the error profile, etc.
 

Diagnoses

The issue was caused by NET CLR Version for K2 Workspace App Pool was set to 4.0.30319.
 

Resolution

Changing the .NET CLR Version for K2 Workspace App Pool to 2.0.50727 resolved the issue.
IIS Manager > Application Pools > right click application pool used for K2 Workspace site > click Basic Settings