{"id":"CVE-2026-53724","aliases":["BIT-parse-2026-53724","GHSA-7wqv-xjf3-x35v"],"url":"https://o3.security/vulnerability/CVE-2026-53724","summary":"Parse Server: Stored XSS via trailing-dot filename bypassing file upload extension blocklist","details":"### Impact\n\nThe default file upload extension blocklist can be bypassed by appending a trailing dot to a filename whose extension would otherwise be blocked (e.g. `poc.svg.`). The trailing dot causes the extension parser to extract an empty string, which short-circuits the blocklist check, and the attacker-controlled Content-Type is forwarded to the storage adapter unchanged. Storage adapters that persist and serve the provided Content-Type (such as S3 or GCS) then serve the file with an active type such as `image/svg+xml`, enabling stored XSS when a victim opens the file URL. The default GridFS adapter is not affected because it sets `X-Content-Type-Options: nosniff` on responses.\n\n### Patches\n\nA filename ending in a dot is now treated as extensionless. When the parser produces an empty extension, the request handler falls back to validating the Content-Type subtype against the configured extension blocklist, matching the path that already catches truly extensionless uploads with a dangerous Content-Type. This is a follow-up to the previous fix [GHSA-vr5f-2r24-w5hc](https://github.com/parse-community/parse-server/security/advisories/GHSA-vr5f-2r24-w5hc).\n\n### Workarounds\n\nConfigure the storage adapter or CDN to derive Content-Type from the filename extension instead of using the stored Content-Type, or replace the default blocklist with an explicit allowlist of needed file extensions.","published":"2026-06-12T18:34:38.237Z","modified":"2026-10-21T02:58:30.182856073Z","cvss":null,"epss":{"score":0.00281,"percentile":0.20723,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"parse-server","fixedVersion":"9.9.1-alpha.4"},{"ecosystem":"npm","name":"parse-server","fixedVersion":"8.6.79"}],"fix":{"url":"https://github.com/parse-community/parse-server/pull/10489","label":"parse-community/parse-server#10489"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53724.json"},{"type":"ADVISORY","url":"https://github.com/parse-community/parse-server/security/advisories/GHSA-7wqv-xjf3-x35v"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53724"},{"type":"FIX","url":"https://github.com/parse-community/parse-server/pull/10489"},{"type":"FIX","url":"https://github.com/parse-community/parse-server/pull/10490"},{"type":"PACKAGE","url":"https://github.com/parse-community/parse-server"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:30.182856073Z"}}