This indicates an attack attempt to exploit a Path Traversal vulnerability in Confluence Server and Data Center.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when handling file attachments requests. A remote attacker may be able to exploit this to write files to arbitrary locations on the systems, leading to possible remote code execution.
2.0.0 <= version < 6.6.13
6.7.0 <= version < 6.12.4
6.13.0 <= version < 6.13.4
6.14.0 <= version < 6.14.3
6.15.0 <= version < 6.15.2
System Compromise: Remote attackers can gain control of vulnerable systems.
Refer to the vendor's advisory for updates: