---
id: CVE-2026-53724
title: >-
  parse-server: Stored XSS via trailing-dot filename bypassing file upload
  extension blocklist
summary: >-
  parse-server: Stored XSS via trailing-dot filename bypassing file upload
  extension blocklist
severity: low
cwe:
  - CWE-79
  - CWE-434
vendor: parse-server
product: parse-server
affected:
  - 'parse-server >= 9.0.0, < 9.9.1-alpha.4'
  - parse-server <= 8.6.78
patched:
  - parse-server 9.9.1-alpha.4
  - parse-server 8.6.79
published: '2026-06-19'
updated: '2026-06-19'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-7wqv-xjf3-x35v'
references:
  - url: >-
      https://github.com/parse-community/parse-server/security/advisories/GHSA-7wqv-xjf3-x35v
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53724'
  - url: 'https://github.com/parse-community/parse-server/pull/10489'
  - url: 'https://github.com/parse-community/parse-server/pull/10490'
  - url: 'https://github.com/advisories/GHSA-7wqv-xjf3-x35v'
tags:
  - ghsa
  - npm
epss: 0.00488
epssPercentile: 0.39449
ingestedAt: '2026-06-22T15:52:21.060Z'
ecosystem: npm
---

## Overview

### Impact

The default file upload extension blocklist can be bypassed by appending a trailing dot to a filename whose extension would otherwise be blocked (e.g. `poc.svg.`). The trailing dot causes the extension parser to extract an empty string, which short-circuits the blocklist check, and the attacker-controlled Content-Type is forwarded to the storage adapter unchanged. Storage adapters that persist and serve the provided Content-Type (such as S3 or GCS) then serve the file with an active type such as `image/svg+xml`, enabling stored XSS when a victim opens the file URL. The default GridFS adapter is not affected because it sets `X-Content-Type-Options: nosniff` on responses.

### Patches

A filename ending in a dot is now treated as extensionless. When the parser produces an empty extension, the request handler falls back to validating the Content-Type subtype against the configured extension blocklist, matching the path that already catches truly extensionless uploads with a dangerous Content-Type. This is a follow-up to the previous fix [GHSA-vr5f-2r24-w5hc](https://github.com/parse-community/parse-server/security/advisories/GHSA-vr5f-2r24-w5hc).

### Workarounds

Configure the storage adapter or CDN to derive Content-Type from the filename extension instead of using the stored Content-Type, or replace the default blocklist with an explicit allowlist of needed file extensions.

## Affected packages

- `parse-server >= 9.0.0, < 9.9.1-alpha.4`
- `parse-server <= 8.6.78`

## Remediation

Upgrade to a patched release:

- `parse-server 9.9.1-alpha.4`
- `parse-server 8.6.79`