CVE-2026-78079 in Helix Ultimate Extension
Summary
by MITRE • 08/31/2026
Joomla Extension - joomshaper.com - Open Redirect via Base64 Return Parameter in Helix Ultimate < 2.2.10 - Return redirect parameters accepted arbitrary Base64 strings without verifying whether the resolved target was an internal site URL via Uri::isInternal.
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Analysis
by VulDB Data Team • 08/31/2026
The vulnerability identified in Joomla extensions hosted on joomshaper.com, specifically within the Helix Ultimate framework prior to version 2.2.10, represents a critical open redirect flaw rooted in improper validation of user-supplied input during authentication or session management flows. The core technical defect lies in the handling of return parameters that are encoded using Base64 encoding. When an application accepts such parameters for redirection purposes after successful login or other state-changing actions, it must rigorously validate whether the decoded target URL points to a trusted internal domain. In this specific instance, the implementation failed to invoke the Uri::isInternal method or equivalent security checks before processing the redirect instruction. This oversight allows attackers to supply arbitrary Base64-encoded strings that decode into external URLs, effectively bypassing any intended restrictions on where users can be redirected after interacting with the application.
From a technical perspective, this flaw exploits the trust relationship between the web server and its own domain by leveraging the client-side browser's navigation capabilities. When an attacker crafts a malicious link containing a Base64-encoded URL pointing to a phishing site or other malicious destination, they can trick users into clicking it within the context of the legitimate Joomla website. Because the redirect occurs from a trusted origin, browsers often display the original domain in the address bar initially, lending false credibility to the subsequent redirection. This technique is particularly dangerous because it bypasses many security filters that rely on simple string matching for known malicious domains, as the payload is obfuscated through Base64 encoding until the moment of execution by the browser or server-side logic.
The operational impact of this vulnerability extends beyond mere navigation hijacking. Open redirects are frequently utilized in sophisticated phishing campaigns to increase their success rate and evade email security gateways that flag suspicious links. By masking a malicious URL behind a legitimate-looking domain, attackers can deceive users into entering sensitive credentials on fake login pages hosted externally. Furthermore, these redirects can be chained with other vulnerabilities or used for cross-site request forgery attacks where the redirect is part of a larger exploit chain designed to manipulate user sessions or execute unauthorized actions under the guise of trusted traffic. The lack of verification against internal URLs means that any external domain becomes a viable target vector, significantly expanding the attack surface available to malicious actors.
This vulnerability aligns with CWE-601, which defines Open Redirect as a flaw where an application redirects users to a URL provided by the user without proper validation. It also maps directly to MITRE ATT&CK technique T1566.002, known as Spearphishing Link, wherein attackers send links that redirect victims to malicious sites designed to steal data or install malware. The failure to use standard security utilities like Uri::isInternal highlights a gap in the application's defensive coding practices, emphasizing the need for strict allow-listing of permitted domains rather than relying on implicit trust mechanisms.
To mitigate this risk, developers must ensure that all redirect parameters are validated against an explicit list of allowed internal domains before processing any redirection logic. Implementing robust input validation at both the client and server sides is essential to prevent malicious payloads from reaching critical decision points in the application flow. Upgrading Helix Ultimate to version 2.2.10 or later resolves this issue by incorporating proper checks that verify whether the resolved target URL belongs to an internal site before executing the redirect. Additionally, implementing Content Security Policy headers can help mitigate some of the downstream effects by restricting where scripts and navigations are allowed to occur, providing a defense-in-depth layer against exploitation even if similar vulnerabilities exist in other components.