CVE-2026-55778
Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
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.
INFO
Published Date :
July 8, 2026, 9:16 p.m.
Last Modified :
July 8, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-55778
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | LOW | [email protected] |
Solution
- Update Parse Server to version 9.9.1-alpha.11.
- Update Parse Server to version 8.6.81.
- Configure file upload restrictions properly.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55778.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55778 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55778
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55778 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55778 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'parse-community', 'product': 'parse-server', 'versions': [{'status': 'affected', 'version': '>= 9.0.0-alpha.1, < 9.9.1-alpha.11'}, {'status': 'affected', 'version': '< 8.6.81'}]}] 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. Added CVSS V4.0 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 Added CWE CWE-434 Added Reference https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a Added Reference https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50 Added Reference https://github.com/parse-community/parse-server/pull/10505 Added Reference https://github.com/parse-community/parse-server/pull/10506 Added Reference https://github.com/parse-community/parse-server/releases/tag/8.6.81 Added Reference https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11 Added Reference https://github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r927-cc93