CVE-2026-107903 in Gridbox Extension
Summary
by MITRE • 11/05/2026
Joomla Extension - balbooa.com - Stored XSS in reviews via inconsistent sanitization in Gridbox < 2.20.5.0
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Analysis
by VulDB Data Team • 11/05/2026
The vulnerability identified as a stored cross-site scripting (XSS) flaw within the Joomla extension developed by Balbooa, specifically affecting versions of Gridbox prior to release 2.20.5.0, represents a significant security risk for web applications utilizing this framework. This issue stems from inconsistent input sanitization mechanisms embedded in the review submission functionality of the application. When users submit reviews through the interface, the system fails to adequately validate or encode special characters within the user-supplied data before storing it in the backend database and subsequently rendering it on public-facing pages. This lack of proper output encoding allows an attacker to inject malicious JavaScript payloads directly into the stored content, which are then executed by the browsers of other users who view the compromised review entries.
From a technical perspective, this vulnerability is classified under CWE-79, commonly known as Improper Neutralization of Input During Web Page Generation, or more specifically Stored Cross-Site Scripting. The root cause lies in the application's failure to implement robust input validation and context-aware output encoding when handling user-generated content within the Gridbox review module. Unlike reflected XSS where malicious scripts are executed immediately via a crafted URL, stored XSS persists on the server side, making it particularly dangerous as every visitor to the affected page becomes a potential victim without any direct interaction with the attacker's initial payload delivery mechanism. The inconsistency in sanitization suggests that while some input fields may be properly secured, others lack these protections, creating an exploitable gap that security researchers and malicious actors can leverage to bypass existing filters.
The operational impact of this vulnerability is severe due to its persistent nature. An authenticated or unauthenticated attacker, depending on the specific configuration and permissions granted by the site administrator for review submissions, can inject scripts that perform a variety of malicious actions. These include stealing session cookies to hijack user accounts, performing actions on behalf of victims such as changing passwords or making purchases, defacing the website's appearance, or redirecting users to phishing sites designed to harvest credentials. Because the payload is stored in the database, it affects all subsequent visitors who load the page containing the malicious review, amplifying the blast radius significantly compared to non-persistent vulnerabilities. This can lead to widespread compromise of user data and erosion of trust in the affected Joomla website.
In terms of industry frameworks, this vulnerability aligns with MITRE ATT&CK technique T1059.007, which covers JavaScript execution within web browsers as part of Command and Control or Collection phases depending on the payload's intent. The attack vector typically involves social engineering to encourage users to visit a page containing the compromised review if direct access is restricted, though in many Joomla configurations, public reviews are visible by default, allowing for passive exploitation. Defense-in-depth strategies must be employed to mitigate this risk effectively.
To remediate this issue, administrators should immediately update their Gridbox extension to version 2.20.5.0 or later, where the developers have addressed the inconsistent sanitization logic and implemented stricter input validation protocols. For organizations unable to patch immediately due to compatibility concerns with other components, temporary mitigations include implementing a Web Application Firewall (WAF) rule set capable of detecting and blocking common XSS payloads in POST requests related to review submissions. Additionally, enabling Content Security Policy headers can help mitigate the impact by restricting the sources from which scripts are allowed to execute, thereby preventing the injected malicious code from running even if it is successfully stored and rendered on the page. Regular security audits and penetration testing of custom Joomla extensions are also recommended to identify similar inconsistencies in input handling across other modules before they can be exploited.