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CVE-2026-55778lowCWE-434

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

8Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 2.1epss 0.6%
exploitation probability
0.6%top 55% of all CVEs
observed exploitation
nono source reports it
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.
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