CVE-2025-15489 in Passster Plugin
Summary
by MITRE • 09/02/2026
The Passster WordPress plugin before 4.2.24 does not handle input properly in an AJAX action, allowing unauthenticated users to retrieve the value of password protected content
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in versions of the Passster WordPress plugin prior to release 4.2.24 represents a critical failure in access control mechanisms within the application's asynchronous JavaScript and XML processing logic. This flaw specifically resides in an AJAX action handler that is designed to manage password-protected content, a feature commonly used by website administrators to restrict visibility of specific posts or pages behind a user-supplied passphrase. The core technical deficiency lies in the insufficient validation of incoming requests against established authentication states. Because the endpoint responsible for retrieving this protected data does not adequately verify whether the requesting entity has successfully authenticated via the standard WordPress password protection mechanism, it effectively bypasses the intended security boundary. This architectural oversight allows any external actor to interact with the backend logic without possessing valid credentials or having previously entered the correct passphrase on the frontend interface.
From a technical perspective, this issue is classified as an Insecure Direct Object Reference combined with Broken Access Control vulnerabilities. The attacker can exploit this by crafting specific HTTP requests that target the vulnerable AJAX endpoint directly. By manipulating parameters such as post IDs or content identifiers, the malicious actor forces the server to process and return the plaintext contents of pages marked for password protection. This behavior contradicts the fundamental security principle that sensitive data must only be accessible to authorized users who have undergone proper verification procedures. The lack of session validation or token-based integrity checks in this specific AJAX routine creates a direct path for unauthorized data exfiltration, rendering the encryption-like barrier provided by WordPress's native password feature ineffective against automated scripts and manual exploitation attempts alike.
The operational impact of this vulnerability is severe, particularly for websites that rely on Passster to safeguard sensitive information such as client details, proprietary business documents, or personal identifiable information. An unauthenticated attacker can systematically enumerate protected content identifiers and retrieve their full textual contents without any friction or detection from standard security logging mechanisms designed to flag failed login attempts. This leads directly to a compromise of confidentiality, one of the three pillars of the CIA triad in cybersecurity. Furthermore, if the password-protected content contains additional links, embedded media, or further exploitable code, this initial breach can serve as a foothold for more advanced attacks, including cross-site scripting or server-side request forgery attempts against downstream systems referenced within the exposed material.
Industry standards provide clear frameworks for understanding and mitigating such flaws. This vulnerability aligns with CWE-284 Improper Access Control and CWE-601 URL Redirection to Untrusted Site Open Redirect if misconfigured, but most accurately maps to CWE-359 Exposure of Private Personal Information or sensitive data through an API endpoint that lacks proper authorization checks. In the context of the MITRE ATT&CK framework for enterprise security, this exploitation technique corresponds to T1078 Valid Accounts when considering the bypass of authentication requirements, and more specifically relates to techniques involving unauthorized access to resources via insecure APIs. Security auditors should treat any AJAX handler in a WordPress plugin that returns sensitive content without verifying session tokens or nonce values as high-risk until proven otherwise through rigorous code review and penetration testing.
To mitigate this risk, immediate action is required by updating the Passster plugin to version 4.2.24 or later, where these access control checks have been implemented in the AJAX handler logic. Administrators who cannot immediately update should consider implementing web application firewall rules that restrict direct access to known vulnerable endpoints unless accompanied by valid WordPress session cookies and nonces. Additionally, developers reviewing similar plugins should enforce strict input validation and ensure that all data retrieval operations verify the user's current authentication state against the specific permissions required for accessing password-protected content. Regular security assessments focusing on API endpoint authorization logic are essential to prevent recurrence of such access control bypasses in WordPress ecosystems.