CVE-2026-16776 in MP3 Audio Player Plugin
Summary
by MITRE • 10/10/2026
The MP3 Audio Player – Music Player, Podcast Player & Radio by Sonaar plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Shortcode Attributes in all versions up to, and including, 5.14.2 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. WordPress's save-time wp_kses_post does not neutralize the payload because the attack is delivered via shortcode attributes rather than raw HTML in post content, allowing the unescaped values to survive to render time.
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Analysis
by VulDB Data Team • 10/10/2026
The vulnerability identified within the MP3 Audio Player plugin for WordPress represents a significant security risk due to its potential for Stored Cross-Site Scripting attacks. This flaw exists across all versions up to and including 5.14.2, stemming from insufficient input sanitization and output escaping mechanisms when processing shortcode attributes. Unlike typical vulnerabilities that affect raw HTML content in posts or comments, this specific issue targets the structural components of WordPress shortcodes, which are used to embed dynamic functionality into pages. The core technical flaw lies in the plugin's failure to properly validate and escape user-supplied data within these attribute fields before storing them in the database and subsequently rendering them on the frontend without adequate protection against script injection.
The operational impact of this vulnerability is severe because it allows authenticated attackers with contributor-level access or higher privileges to inject arbitrary web scripts into pages managed by the site. When a victim, such as an administrator or another user with viewing rights, accesses a page containing the malicious shortcode, the injected JavaScript executes in their browser context. This execution occurs within the security domain of the WordPress installation, granting the attacker the ability to perform actions on behalf of the victim, steal session cookies, hijack administrative sessions, deface websites, or redirect users to phishing sites. The persistence of this attack vector is particularly dangerous because the malicious code remains stored in the database and executes every time the affected page is loaded by any user with access permissions.
A critical aspect of this vulnerability's success is its ability to bypass WordPress's standard save-time sanitization function, wp_kses_post. This built-in security feature is designed to strip out potentially harmful HTML tags and attributes from post content during the saving process. However, because the attack payload is delivered via shortcode attributes rather than raw HTML embedded directly in the post body, it evades detection by this specific filter. The plugin fails to apply equivalent sanitization logic to its own attribute parsing routines, allowing unescaped values to survive the save operation and persist until render time when they are outputted without escaping. This architectural oversight creates a gap between general WordPress security measures and plugin-specific input handling practices.
From an industry standards perspective, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. Specifically, it falls under the subcategory of Stored XSS where malicious scripts are permanently stored within target applications. In terms of attack tactics, this behavior corresponds to MITRE ATT&CK technique T1059, Command and Scripting Interpreter, particularly when used for client-side script execution such as JavaScript or VBScript. The exploitation relies on social engineering or privilege escalation if the attacker does not already possess contributor-level access, making it a high-value target for threat actors seeking persistent footholds within WordPress ecosystems.
Mitigation strategies should prioritize immediate updates to version 5.14.3 or later where this issue has been addressed by the developers through improved input validation and output escaping protocols. For organizations unable to update immediately due to compatibility constraints, implementing Web Application Firewall rules can help detect and block attempts to inject malicious scripts via shortcode attributes. Additionally, enforcing strict role-based access control is essential; administrators should ensure that only trusted users with verified credentials are granted contributor-level or higher privileges. Regular security audits of custom plugins and third-party extensions are also recommended to identify similar gaps in input sanitization logic before they can be exploited by adversaries seeking to compromise WordPress environments.