Sickbeard through build-507 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to inject scripts through the pattern parameter of /config/postProcessing/testNaming. Attackers can craft GET requests with malicious SVG onload payloads that the testNaming handler returns unescaped, executing JavaScript in victims' browsers. Exploitation evidence was first observed by the Shadowserver Foundation on 2023-10-22.