CVE-2026-55778
Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
- State
- Published
- Severity
- 2.1 Low
- Published
- Jul 8, 2026
- Updated
- Jul 9, 2026
- Reserved
- Jun 17, 2026
Description
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.9.1-alpha.11 and 8.6.81, the default fileUpload.fileExtensions blocklist could be bypassed by uploading a file with a non-standard or compound extension and dangerous content type, allowing storage adapters such as S3 and GCS to serve attacker-supplied active content and enable stored cross-site scripting. This issue is fixed in versions 9.9.1-alpha.11 and 8.6.81.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 2.1 Low | CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N | GitHub_M |
Weaknesses
- CWE-434 Unrestricted Upload of File with Dangerous Type
Affected Products
| Product | Versions |
|---|---|
parse-serverparse-community |
|
References
- https://github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r927-cc93
- https://github.com/parse-community/parse-server/pull/10505
- https://github.com/parse-community/parse-server/pull/10506
- https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a
- https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50
- https://github.com/parse-community/parse-server/releases/tag/8.6.81
- https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11
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