What’s Vulnerable › Vulnerabilities

CVE-2026-53724: Parse Server: Stored XSS via trailing-dot filename bypassing file upload extension blocklist

• Severity: low (CVSS 2.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-12 · updated 2026-10-26
• Weakness: CWE-79

Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.79 and 9.9.1-alpha.4, the 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. This issue has been patched in versions 8.6.79 and 9.9.1-alpha.4.

Affected products

• parse-community parse-server: before 8.6.79; from 9.0.0, < 9.9.1-alpha.4

References

• https://github.com/parse-community/parse-server/pull/10489
• https://github.com/parse-community/parse-server/pull/10490
• https://github.com/parse-community/parse-server/security/advisories/GHSA-7wqv-xjf3-x35v

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