CVE-2026-55778
LOWParse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
Title source: cnaDescription
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.
References (7)
Core 7
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r927-cc93
X_Refsource_Misc x_refsource_misc
https://github.com/parse-community/parse-server/pull/10505
X_Refsource_Misc x_refsource_misc
https://github.com/parse-community/parse-server/pull/10506
X_Refsource_Misc x_refsource_misc
https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a
X_Refsource_Misc x_refsource_misc
https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50
X_Refsource_Misc x_refsource_misc
https://github.com/parse-community/parse-server/releases/tag/8.6.81
X_Refsource_Misc x_refsource_misc
https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11
Scores
CVSS v4
2.1
EPSS
0.0041
EPSS Percentile
33.4%
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-434
Status
published
Products (2)
parse-community/parse-server
< 8.6.81
parse-community/parse-server
>= 9.0.0-alpha.1, < 9.9.1-alpha.11
Published
Jul 08, 2026
Tracked Since
Jul 09, 2026