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

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,...

CVE-2026-55778

Parse Server is affected by a stored XSS vulnerability where the default fileUpload.fileExtensions blocklist can be bypassed using non-standard or compound extensions paired with a dangerous Content-Type. This enables attacker-supplied content to be served by storage adapters (e.g., S3, GCS) and ...

parse-server: Stored XSS via non-standard file extension bypassing file upload extension blocklist

Impact Parse Server's default fileUpload.fileExtensions blocklist is intended to prevent uploading files that browsers render as active content such as HTML and SVG, which can be used to perform stored cross-site scripting XSS attacks against other users. The blocklist could be bypassed by...