inversoft prime-jwt version prior to version 1.3.0 or prior to commit 0d94dcef0133d699f21d217e922564adbb83a227 contains an input validation vulnerability in JWTDecoder.decode that can result in a JWT that is decoded and thus implicitly validated even if it lacks a valid signature. This attack appear to be exploitable via an attacker crafting a token with a valid header and body and then requests it to be validated. This vulnerability appears to have been fixed in 1.3.0 and later or after commit 0d94dcef0133d699f21d217e922564adbb83a227.