CVE-2026-55778

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

Published Jul 8, 2026 CVSS 4.0 · 2.1 Low EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-v8x7-r927-cc93 parse-server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Parse Community
Parse Community parse Server
Vendors & Products Parse Community
Parse Community parse Server
Type Values Removed Values Added
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.
Title Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
Weaknesses CWE-434
References
Metrics cvssV4_0

{'score': 2.1, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 9, 2026, 1:39 PM
Reserved
Jun 17, 2026, 2:40 PM
Status
Deferred
Published
Jul 8, 2026, 9:16 PM
Modified
Oct 25, 2026, 5:10 PM