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CVE-2026-74253 – Unauthenticated Remote Code Execution – Sourcerer extension for Joomla (versions 1.

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Summary

CVE-2026-74253 is a critical, unauthenticated remote code execution vulnerability in the Sourcerer extension for Joomla, developed by Regular Labs. The flaw stems from improper control of code generation (CWE-94): Sourcerer processes {source} blocks found anywhere in Joomla’s final rendered HTML output without reliably verifying where that code actually originated, allowing an attacker to smuggle in and execute arbitrary code without any authentication. The vulnerability carries the maximum CVSS score of 10.0 and affects all Sourcerer versions from 1.0.0 through 13.1.1.

Technical details

  • Root cause: Sourcerer scans Joomla’s fully rendered HTML for {source} tags and executes the embedded code (including PHP), but it does not reliably distinguish between code that was legitimately authored/verified within trusted content (e.g., articles created by Super Users) and code that was reflected or injected into the page output through other means (e.g., search results, AJAX responses, module output, or other unverified rendering paths).
  • Trigger conditions: Any mechanism that causes attacker-controlled input containing a {source} block to appear in the site’s final rendered HTML can cause Sourcerer to treat it as legitimate embedded code and execute it.
  • Attack vector: Network — the vulnerability can be exploited remotely, requires no privileges, and requires no user interaction.
  • Impact: Full compromise of confidentiality, integrity, and availability of the affected Joomla site, since arbitrary PHP/code execution on the web server is possible without authentication.

Affected software

  • Sourcerer extension for Joomla (developed by Regular Labs), versions 1.0.0 through 13.1.1

Severity

  • CVSS Score: 10.0 (Critical)
  • CVSS v4.0 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
  • Weakness: CWE-94 (Improper Control of Generation of Code) / CAPEC-242 (Code Injection)

Mitigation and recommended actions

  • Immediate: Upgrade Sourcerer to version 14.0.0 or later, which contains the vendor-designated security fix that "prevents reflected or otherwise unverified rendered Sourcerer code from executing by default while preserving verified article and Custom module code."
  • Note that the 14.0.0 update introduces backward-compatibility breaks: previously trusted Sourcerer output generated only during component, module, head, or final rendering may be removed by default, and Pro sites must explicitly opt in to allow unverified CSS, JavaScript, or PHP code. Administrators should review Sourcerer security settings after upgrading to confirm intended behavior is preserved.
  • If immediate patching is not possible: Restrict or disable Sourcerer in any component, module, or content area accessible to non-trusted or non-backend users, and audit existing site content for injected {source} blocks in areas that accept user-submitted or reflected input.

References

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