ONLYOFFICE DocumentServer before 10.0.0 SSRF via downloadfile isInJwtToken Bypass

ONLYOFFICE DocumentServer before 10.0.0 contains an unauthenticated server-side request forgery vulnerability in the /downloadfile/:docid endpoint that allows remote attackers to bypass the private-IP request-filtering-agent by exploiting the isInJwtToken flag when JWT verification is disabled in the default configuration. Attackers can submit a crafted request body containing an internal or loopback URL, which is treated as a DIRECT request skipping private-address filtering, causing the server to fetch and proxy back arbitrary private-network and cloud metadata content.