danmuapi before 1.21.7 contains an authentication bypass vulnerability that allows unauthenticated attackers to modify server environment configuration when the default TOKEN is used and ADMINTOKEN is unset. Attackers can send POST requests to /api/env/set, /api/env/add, or /api/env/del to set ADMINTOKEN, lock out operators, redirect OTHERSERVER or PROXYURL for SSRF, and trigger redeployment.