Bagisto has HTML Filter Bypass that Enables Stored XSS

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.2 · CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:P · score source

EPSS

• CVE-2026-21451: 0.56% estimated exploitation activity in the next 30 days; percentile 46.45 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A stored Cross-Site Scripting (XSS) vulnerability exists in Bagisto 2.3.8 within the CMS page editor. Although the platform normally attempts to sanitize <script tags, the filtering can be bypassed by manipulating the raw HTTP POST request before submission. As a result, arbitrary JavaScript can be stored in the CMS content and executed whenever the page is viewed or edited. This exposes administrators to a high-severity risk, including complete account takeover, backend hijacking, and malicious script execution. Details Bagisto’s CMS editor includes an HTML sanitation mechanism intended to protect against script injection by wrapping raw script content in <div elements. However, this mechanism is applied only to requests submitted through the UI. When the CMS update request is intercepted and modified at the HTTP level, the sanitation layer fails to strip or encode embedded <script tags. Because the back-end trusts the manipulated request, the malicious script is stored in…

Published by the source

2 Jan 2026, 21:16 UTC

Last modified by the source

3 Jan 2026, 00:33 UTC

Source last checked

26 Oct 2026, 14:35 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2mwc-h2mg-v6p8

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# Patch Next advisory brief: CVE-2026-21451

Advisory: Bagisto has HTML Filter Bypass that Enables Stored XSS
IDs: CVE-2026-21451, GHSA-2mwc-h2mg-v6p8
Record: https://patchnext.com/advisories/cve-2026-21451 (revision 1, source checked 26 Oct 2026, 14:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: bagisto/bagisto 2.3.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist bagisto/bagisto: affected < 2.3.10; fixed in 2.3.10

## Suggested inspection (read-only)
- Packagist bagisto/bagisto: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on bagisto/bagisto.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2mwc-h2mg-v6p8 (GitHub-reviewed advisory GHSA-2mwc-h2mg-v6p8 lists affected ranges: Packagist bagisto/bagisto >=0 <2.3.10)

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