PolarLearn's unvalidated vote direction allows vote count manipulation

PolarLearn is a free and open-source learning program. Prior to version 0-PRERELEASE-15, the vote API route (POST /api/v1/forum/vote) trusts the JSON body’s direction value without runtime validation. TypeScript types are not enforced at runtime, so an attacker can send arbitrary strings (e.g., "x") as direction. Downstream (VoteServer) treats any non-"up" and non-null value as a downvote and persists the invalid value in votes_data. This can be exploited to bypass intended business logic. Version 0-PRERELEASE-15 fixes the vulnerability.