Dalfox is a powerful open-source XSS scanner and utility focused on automation. Prior to 2.13.0, when dalfox is run in REST API server mode, the custom-payload-file field in model.Options is JSON-tagged and deserialized directly from the attacker's request body, then propagated unchanged through dalfox.Initialize into the scan engine. The engine passes the value to voltFile.ReadLinesOrLiteral, which reads lines from any file path accessible to the dalfox process and embeds each line as an XSS payload in outbound HTTP requests directed at the attacker-controlled target URL. Because the server has no API key by default, an unauthenticated network attacker can exfiltrate the contents of arbitrary files on the dalfox host by reading them line-by-line through scan traffic. This vulnerability is fixed in 2.13.0.