parse-community parse-server up to 8.6.40/9.6.0-alpha.14 File Extension cross site scripting

Summaryinfo

A vulnerability, which was classified as problematic, has been found in parse-community parse-server up to 8.6.40/9.6.0-alpha.14. This affects an unknown part of the component File Extension Handler. Performing a manipulation results in cross site scripting. This vulnerability is cataloged as CVE-2026-32728. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in parse-community parse-server up to 8.6.40/9.6.0-alpha.14. This affects an unknown functionality of the component File Extension Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. The summary by CVE is:

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.15 and 8.6.41, an attacker who is allowed to upload files can bypass the file extension filter by appending a MIME parameter (e.g. `;charset=utf-8`) to the `Content-Type` header. This causes the extension validation to fail matching against the blocklist, allowing active content to be stored and served under the application's domain. In addition, certain XML-based file extensions that can render scripts in web browsers are not included in the default blocklist. This can lead to stored XSS attacks, compromising session tokens, user credentials, or other sensitive data accessible via the browser's local storage. The fix in versions 9.6.0-alpha.15 and 8.6.41 strips MIME parameters from the `Content-Type` header before validating the file extension against the blocklist. The default blocklist has also been extended to include additional XML-based extensions (`xsd`, `rng`, `rdf`, `rdf+xml`, `owl`, `mathml`, `mathml+xml`) that can render active content in web browsers. Note that the `fileUpload.fileExtensions` option is intended to be configured as an allowlist of file extensions that are valid for a specific application, not as a denylist. The default denylist is provided only as a basic default that covers most common problematic extensions. It is not intended to be an exhaustive list of all potentially dangerous extensions. Developers should not rely on the default value, as new extensions that can render active content in browsers might emerge in the future. As a workaround, configure the `fileUpload.fileExtensions` option to use an allowlist of only the file extensions that your application needs, rather than relying on the default blocklist.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-32728 since 03/13/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 8.6.41 or 9.6.0-alpha.15 eliminates this vulnerability. Applying the patch 4f53ab3cad5502a51a509d53f999e00ff7217b8d is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• parse-community

Name

• parse-server

Version

• 8.6.0
• 8.6.1
• 8.6.2
• 8.6.3
• 8.6.4
• 8.6.5
• 8.6.6
• 8.6.7
• 8.6.8
• 8.6.9
• 8.6.10
• 8.6.11
• 8.6.12
• 8.6.13
• 8.6.14
• 8.6.15
• 8.6.16
• 8.6.17
• 8.6.18
• 8.6.19
• 8.6.20
• 8.6.21
• 8.6.22
• 8.6.23
• 8.6.24
• 8.6.25
• 8.6.26
• 8.6.27
• 8.6.28
• 8.6.29
• 8.6.30
• 8.6.31
• 8.6.32
• 8.6.33
• 8.6.34
• 8.6.35
• 8.6.36
• 8.6.37
• 8.6.38
• 8.6.39
• 8.6.40
• 9.6.0-alpha.0
• 9.6.0-alpha.1
• 9.6.0-alpha.2
• 9.6.0-alpha.3
• 9.6.0-alpha.4
• 9.6.0-alpha.5
• 9.6.0-alpha.6
• 9.6.0-alpha.7
• 9.6.0-alpha.8
• 9.6.0-alpha.9
• 9.6.0-alpha.10
• 9.6.0-alpha.11
• 9.6.0-alpha.12
• 9.6.0-alpha.13
• 9.6.0-alpha.14

License

• open-source

Website

• Product: https://github.com/parse-community/parse-server/

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