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6.3
Parse Server allows attackers to steal user data via uploaded files
GHSA-v5hf-f4c3-m5rv
CVE-2026-31868
Summary
A security weakness in Parse Server allows attackers to upload files that can be used to steal user data, redirect users, or take actions on other users' accounts. This affects Parse Server users who allow file uploads. To fix this, update to the latest version of Parse Server or block the affected file types in your server settings.
What to do
- Update parse-server to version 9.6.0-alpha.4.
- Update parse-server to version 8.6.30.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| – | parse-server | > 9.0.0-alpha.1 , <= 9.6.0-alpha.4 | 9.6.0-alpha.4 |
| – | parse-server | <= 8.6.30 | 8.6.30 |
Original title
Parse Server vulnerable to stored XSS via file upload of HTML-renderable file types
Original description
### Impact
An attacker can upload a file with a file extension or content type that is not blocked by the default configuration of the Parse Server `fileUpload.fileExtensions` option. The file can contain malicious code, for example JavaScript in an SVG or XHTML file. When the file is accessed via its URL, the browser renders the file and executes the malicious code in the context of the Parse Server domain. This is a stored Cross-Site Scripting (XSS) vulnerability that can be exploited to steal session tokens, redirect users, or perform actions on behalf of other users.
Affected file extensions and content types include `.svgz`, `.xht`, `.xml`, `.xsl`, `.xslt`, and content types `application/xhtml+xml` and `application/xslt+xml` for extensionless uploads. Uploading of `.html`, `.htm`, `.shtml`, `.xhtml`, and `.svg` files was already blocked.
### Patches
The fix adds the missing file extensions and content types to the default value of the `fileUpload.fileExtensions` server option.
### Workarounds
Configure the `fileUpload.fileExtensions` server option to block the affected file extensions and content types.
### References
- GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-v5hf-f4c3-m5rv
- Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.6.0-alpha.4
- Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.30
An attacker can upload a file with a file extension or content type that is not blocked by the default configuration of the Parse Server `fileUpload.fileExtensions` option. The file can contain malicious code, for example JavaScript in an SVG or XHTML file. When the file is accessed via its URL, the browser renders the file and executes the malicious code in the context of the Parse Server domain. This is a stored Cross-Site Scripting (XSS) vulnerability that can be exploited to steal session tokens, redirect users, or perform actions on behalf of other users.
Affected file extensions and content types include `.svgz`, `.xht`, `.xml`, `.xsl`, `.xslt`, and content types `application/xhtml+xml` and `application/xslt+xml` for extensionless uploads. Uploading of `.html`, `.htm`, `.shtml`, `.xhtml`, and `.svg` files was already blocked.
### Patches
The fix adds the missing file extensions and content types to the default value of the `fileUpload.fileExtensions` server option.
### Workarounds
Configure the `fileUpload.fileExtensions` server option to block the affected file extensions and content types.
### References
- GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-v5hf-f4c3-m5rv
- Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.6.0-alpha.4
- Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.30
ghsa CVSS4.0
6.3
Vulnerability type
CWE-79
Cross-site Scripting (XSS)
- https://github.com/parse-community/parse-server/security/advisories/GHSA-v5hf-f4...
- https://github.com/parse-community/parse-server/releases/tag/8.6.30
- https://github.com/parse-community/parse-server/releases/tag/9.6.0-alpha.4
- https://github.com/advisories/GHSA-v5hf-f4c3-m5rv
- https://nvd.nist.gov/vuln/detail/CVE-2026-31868
Published: 11 Mar 2026 · Updated: 13 Mar 2026 · First seen: 11 Mar 2026