Low severity · published Jul 8, 2026
CVE-2026-55778
Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
2.1
CVSS
0.6%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 46% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PA
parse-server · parse-community
>= 9.0.0-alpha.1, < 9.9.1-alpha.11; < 8.6.81 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55778
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55778
github.com
https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a
github.com
https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50
github.com
https://github.com/parse-community/parse-server/pull/10505
github.com
https://github.com/parse-community/parse-server/pull/10506
github.com
https://github.com/parse-community/parse-server/releases/tag/8.6.81
github.com
https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11
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