CVE-2026-88853 in Modals Pro Extension
Summary
by MITRE • 09/14/2026
Joomla Extension - regularlabs.com - Privileged stored XSS via event handler option in Modals Pro extension for Joomla < 17.0.0 - Modals Pro intentionally supports JavaScript Events such as on-open and on-closed. Affected versions do not distinguish trusted extension configuration from event code supplied in ordinary article content. A lower-privileged author can therefore use a documented executable feature which should be reserved for trusted authors.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/14/2026
The vulnerability identified involves a privileged stored cross-site scripting (XSS) flaw within the Modals Pro extension for Joomla, specifically affecting versions prior to 17.0.0 developed by regularlabs.com. This security issue stems from an improper separation of privileges and insufficient input validation regarding JavaScript event handlers. The extension is designed to support dynamic behavior through configurable JavaScript events such as on-open and on-closed, which allow developers or site administrators to inject custom scripts that execute when specific modal windows are opened or closed. While this functionality provides significant flexibility for advanced users, the implementation fails to distinguish between trusted configuration inputs provided by high-privileged users and untrusted content supplied by lower-privileged authors through standard article editing interfaces.
In a typical Joomla environment, different user groups possess varying levels of access rights. Administrators and super administrators are expected to handle complex configurations involving code execution, while regular authors or editors should be restricted from executing arbitrary scripts on the server side or in the context of other users' browsers. The flaw arises because the extension processes event handler options without adequately sanitizing or validating the input when it originates from content authored by lower-privileged accounts. Consequently, an attacker with author-level permissions can embed malicious JavaScript code within article content that utilizes these modal features. When a victim user views this content and interacts with the affected modals, the injected script executes in their browser session.
This stored XSS vulnerability poses significant operational risks to web applications running Joomla. Since the malicious payload is stored on the server as part of legitimate content, it persists until removed by an administrator. This persistence allows for persistent attacks against multiple users who view the compromised article. The impact includes potential theft of administrative credentials through cookie or session hijacking, defacement of the website interface, redirection to phishing sites, and execution of arbitrary commands within the context of the victim's browser environment. Furthermore, if the attacker can escalate privileges by stealing an administrator's session token, they may gain full control over the Joomla installation, leading to complete site compromise including database manipulation and server-side file inclusion attacks depending on other existing vulnerabilities.
From a classification perspective, this vulnerability aligns with CWE-79 Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting (XSS). Specifically, it represents a stored variant where the malicious script is permanently stored within target databases or content management systems. In terms of attack vectors and tactics, this flaw facilitates techniques associated with MITRE ATT&CK ID T1059 Command and Scripting Interpreter for executing arbitrary code via browser-based scripts, and potentially T1534 Internal Spearphishing if used to steal credentials from internal users. The core issue is a failure in access control logic where the system does not enforce strict boundaries between trusted configuration data and untrusted user-generated content regarding executable features.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary solution is to upgrade the Modals Pro extension to version 17.0.0 or later, as this release presumably includes patches for input validation and privilege separation. For organizations unable to update immediately due to compatibility constraints, temporary workarounds should be implemented at the web application firewall level to block requests containing suspicious JavaScript event handler patterns in article content fields. Additionally, administrators should review user permissions within Joomla to ensure that only trusted users with administrative or super-administrator roles have access to features involving code execution or complex modal configurations. Content filtering plugins can also be employed to strip out script tags and event attributes from rich text editors used by lower-privileged authors. Regular security audits of third-party extensions are essential to identify similar privilege escalation flaws where documented executable features are exposed to untrusted inputs without adequate sanitization mechanisms.