The vulnerability is present in the ‘/addJugador’ endpoint: * The 'keyJugador' and 'keyJugadorObjectiu' parameters allow the modification of other users’ information without requiring prior authorization validation. This could enable an authenticated attacker to alter any user’s ID and change their information. * The ‘punts’ and ‘numObjectiusEliminats’ fields allow arbitrary data to be added because user input is not properly validated. This makes it possible to obtain authentic prizes, awarded by city councils, by falsifying game scores. * In the ‘tokens’ field, administrative privileges can be self-assigned without server validation or prior authentication. This vulnerability could allow an authenticated attacker to grant themselves administrator permissions and thus escalate privileges. * Numeric fields allow the entry of extremely long values, which can cause the system to crash. Successful exploitation of this vulnerability could allow an authenticated attacker to launch a denial-of-service (DoS) attack, preventing created games from being playable. * The ‘urlImatge’ parameter allows server-side requests to arbitrary URLs, enabling the retrieval of users’ internal IP addresses, access to internal services, reading of local files, and unauthorized interaction with third-party APIs. An authenticated attacker could gain access to sensitive data.