Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

CVE-2026-55778Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist

Low 2.1

In plain English

A low-severity unrestricted file upload in parse-server from parse-community. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 46% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)2.1Low

Exploit odds (30 days)0.6%top 53.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	parse-server	9.9.1-alpha.11	GHSA-v8x7-r927-cc93
npm	parse-server	8.6.81	GHSA-v8x7-r927-cc93

Affected products (as reported)

Vendor	Product	Versions
parse-community	parse-server	>= 9.0.0-alpha.1, < 9.9.1-alpha.11< 8.6.81

Weakness: CWE-434 · Vector: 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

References

https://github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r927-cc93 x_refsource_CONFIRM
https://github.com/parse-community/parse-server/pull/10505 x_refsource_MISC
https://github.com/parse-community/parse-server/pull/10506 x_refsource_MISC
https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a x_refsource_MISC
https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50 x_refsource_MISC
https://github.com/parse-community/parse-server/releases/tag/8.6.81 x_refsource_MISC
https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11 x_refsource_MISC