A backslash authority confusion exists in the header-based Jira and Confluence URL authentication flow. The `validate url for ssrf()` function interprets the authority of a URL differently than the Requests connection layer. By using a crafted URL containing a backslash before userinfo-like syntax, an attacker can bypass SSRF (Server-Side Request Forgery) protections. In this scenario, the validation function identifies an external hostname as the target, while the HTTP client connects to an internal host, allowing unauthorized server-side requests to protected network resources, such as loopback or internal services. This issue can be triggered via the `POST /mcp` endpoint by providing a malicious URL in the `X-Atlassian-Jira-Url` or `X-Atlassian-Confluence-Url` headers.