Connected and Automated Vehicles (CAV) use sensors and wireless communication to improve road safety and efficiency. However, attackers may target Vehicle-to-Everything (V2X) communication. Indeed, an attacker may send authenticated-but-wrong data to send false location information, alert incorrect events, or report a bogus object endangering safety of other CAVs. Standardization Development Organizations (SDO) are currently working on developing security standards against such attacks. Unfortunately, current standardization efforts do not include misbehavior specifications for advanced V2X services such as Maneuver Sharing and Coordination Service (MSCS). This work assesses the security of MSC Messages (MSCM) and proposes inputs for consideration in existing standards.