# CVE-2026-11434: FluentCMS stored XSS in Blocks Plugin

Source: https://junglewise.ai/threats/cve-2026-11434-fluentcms-stored-xss-in-blocks-plugin  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-06. Updated: 2026-06-06  
License: CC BY 4.0 with a link back

CVE-2026-11434 · Severity: low · CVSS 2.4 · Published 2026-06-06

FluentCMS, a content management system, contains a security flaw in its Blocks Plugin component. An attacker with administrative access can inject malicious scripts into website blocks, which then execute in the browsers of other users who visit the site. This could lead to unauthorized actions being performed on behalf of users, session hijacking, or the theft of sensitive information.

Technologies: [Fluentcms](https://junglewise.ai/threats/technologies/fluentcms). Vendors: [Fluentcms](https://junglewise.ai/threats/vendors/fluentcms).

## Quick answers

**Is CVE-2026-11434 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-11434 being exploited in the wild.

**How severe is CVE-2026-11434?** Low severity, with a CVSS score of 2.4, published 6 June 2026.

**Which products and versions are affected?** Fluentcms 0.0.5.

**Is there a fix for CVE-2026-11434?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-11434 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-11434?** Check whether you run Fluentcms at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stored cross-site scripting (XSS) vulnerability exists in FluentCMS 0.0.5 within the Blocks Plugin. The application fails to properly sanitize user-supplied input in the 'Content' field when creating or editing blocks via the /admin/blocks interface. An attacker with high privileges (admin) can inject a malicious JavaScript payload that is stored on the server. When a victim views a page containing the compromised block, the script executes in their browser context. This can be used to steal session cookies or perform unauthorized actions. The vendor was notified but did not respond; a public exploit is available.

## Affected products

- FluentCMS FluentCMS 0.0.5

## Timeline

- 2026-06-06: disclosed: Public disclosure and exploit release
- 2026-06-06: advisory: NVD publication date

## References

- [https://hackmd.io/@noka/BkHdIMFAWx](https://hackmd.io/@noka/BkHdIMFAWx)
- [https://vuldb.com/cve/CVE-2026-11434](https://vuldb.com/cve/CVE-2026-11434)
- [https://vuldb.com/submit/821094](https://vuldb.com/submit/821094)
- [https://vuldb.com/vuln/369014](https://vuldb.com/vuln/369014)
- [https://vuldb.com/vuln/369014/cti](https://vuldb.com/vuln/369014/cti)

## Related threats

- [FluentCMS cross-tenant authorization bypass in PermissionManager](https://junglewise.ai/threats/cve-2026-86271-fluentcms-cross-tenant-authorization-bypass-in-permissionmanager)
- [FluentCMS stored XSS via SVG upload in File Management](https://junglewise.ai/threats/cve-2025-70842-fluentcms-stored-xss-via-svg-upload-in-file-management)
- [FluentCMS TextHTML plugin Cross-Site Scripting in page preview](https://junglewise.ai/threats/cve-2026-38947-fluentcms-texthtml-plugin-cross-site-scripting-in-page-preview)
- [FluentCMS stored XSS via SVG upload in File Management](https://junglewise.ai/threats/cve-2025-15549-fluentcms-stored-xss-via-svg-upload-in-file-management)
- [A cross-site scripting (XSS) vulnerability was identified in FluentCMS 1.2.3. After logging in as an admin and navigating to the "Add Page"](https://junglewise.ai/threats/cve-2025-67349-a-cross-site-scripting-xss-vulnerability-was-identified-in)