GHSA-QGC9-P7CJ-JVH6 FeehiCMS fails to enforce server-side immutability

FeehiCMS version 2.1.1 fails to enforce server-side immutability for parameters that are presented to clients as "read-only." An authenticated attacker can intercept and modify the parameter in transit and the backend accepts the changes. This can lead to unintended username changes...