This indicates an attack attempt to exploit a Command Injection Vulnerability in WebSVN.
The vulnerability is due to insufficient input validation of the requests submitted to Search.php. A remote, unauthenticated attacker can exploit the vulnerability by sending crafted requests to the server. Successful exploitation could result in arbitrary command execution with web server privileges on the target server.
WebSVN before 2.6.1
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.