CVE-2026-78293 in W3all phpBB Plugin
Summary
by MITRE • 08/27/2026
Unauthenticated Cross Site Scripting (XSS) in WP w3all phpBB <= 3.0.6 versions.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified as an unauthenticated cross-site scripting flaw within the WP w3all plugin for WordPress, specifically affecting versions up to and including 3.0.6, represents a significant security risk due to its lack of authentication requirements. This particular class of vulnerabilities allows attackers to inject malicious client-side scripts into web pages viewed by other users without needing valid credentials or prior access to the system. The presence of this flaw indicates that input validation mechanisms are either insufficient or entirely absent in specific endpoints handled by the plugin, which serves as a bridge between WordPress and phpBB forums. By exploiting this weakness, an attacker can execute arbitrary JavaScript code within the context of the victim's browser session, leading to potential compromise of user data and system integrity.
From a technical perspective, the root cause lies in the improper neutralization of special elements used by cross-site scripting attacks within the input fields or parameters processed by WP w3all. When user-supplied data is reflected back into the web page without proper sanitization or encoding, it allows for the injection of script tags and event handlers. This aligns with CWE-79, which categorizes improper neutralization of input during web page generation as a critical weakness in web application security frameworks. The absence of authentication means that any internet user can trigger this vulnerability simply by crafting a malicious URL or submitting a specially formed request to the affected plugin endpoints. This lowers the barrier for entry significantly compared to authenticated XSS vulnerabilities, making it highly attractive for automated scanning tools and opportunistic attackers seeking quick compromises.
The operational impact of such an unauthenticated XSS attack is severe and multifaceted. Once executed in the victim's browser, the malicious script can perform a variety of harmful actions depending on what permissions the logged-in user possesses within both WordPress and phpBB environments. Common consequences include session hijacking, where the attacker steals authentication cookies to impersonate legitimate users; keylogging, which captures sensitive information such as passwords and personal data entered into forms; and defacement of forum posts or website content by manipulating the DOM structure. Furthermore, this vulnerability can be leveraged in conjunction with other attacks like cross-site request forgery to force authenticated actions on behalf of victims without their knowledge. The ability to execute scripts unauthenticated also facilitates drive-by download attempts if combined with browser-specific exploits, potentially leading to malware installation on client machines.
In terms of industry mapping, this vulnerability corresponds directly to the MITRE ATT&CK technique T1059.007, which covers JavaScript execution as a method for achieving initial access or further exploitation within web applications. It also relates to TA0001 Initial Access and TA0005 Defense Evasion depending on how the payload is delivered and executed. The lack of authentication requirement places it in high severity categories according to most scoring systems because it does not require privilege escalation steps prior to exploitation. Organizations relying on this plugin must recognize that even if their WordPress installation has strong access controls, the integration layer with phpBB introduces a separate attack surface that bypasses these protections entirely due to its open nature.
Mitigation strategies for this vulnerability involve immediate remediation through software updates and rigorous input validation practices. The primary solution is to upgrade WP w3all to version 3.0.7 or later where the developers have presumably addressed the input sanitization issues responsible for allowing script injection. Until an update is applied, administrators should consider disabling the plugin if it is not strictly necessary for their operations. Additionally implementing a Web Application Firewall can provide some level of protection by detecting and blocking common XSS payloads in HTTP requests before they reach the application logic. It is also advisable to enforce Content Security Policy headers that restrict script execution sources, thereby limiting the damage even if an injection attempt succeeds. Regular security audits focusing on integration points between disparate systems like WordPress and phpBB are essential to identify similar unauthenticated flaws across other plugins or themes in use.