This indicates an attack attempt to exploit a Privilege Escalation vulnerability in Synology Photo Station.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. A remote attacker may be able to exploit this to escalate their privileges on vulnerable systems.
Photo Station before 6.7.3-3432 and 6.3-2967
Privilege Escalation: Remote attackers can leverage their privileges on vulnerable systems.
Refer to the vendor's advisory for updates: