CVE-2026-1503 in login_register Plugin
Summary
by MITRE • 03/21/2026
The login_register plugin for WordPress is vulnerable to Cross-Site Request Forgery to Stored Cross-Site Scripting in all versions up to, and including, 1.2.0. This is due to missing nonce validation on the settings page and insufficient input sanitization and output escaping on the 'login_register_login_post' parameter. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page via a forged request granted they can trick an administrator into performing an action such as clicking on a link.
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Analysis
by VulDB Data Team • 03/27/2026
The vulnerability identified as CVE-2026-1503 affects the login_register plugin for WordPress, representing a critical security flaw that combines cross-site request forgery and stored cross-site scripting conditions. This vulnerability exists in all versions up to and including 1.2.0, creating a persistent threat vector that can be exploited by unauthenticated attackers to compromise user sessions and execute malicious code within the context of affected websites. The flaw stems from inadequate security controls that fail to properly validate user requests and sanitize input data, creating an exploitable gap in the plugin's defensive mechanisms.
The technical root cause of this vulnerability lies in the absence of nonce validation on the plugin's settings page, which serves as a fundamental security control for verifying legitimate user actions. Additionally, the plugin fails to implement proper input sanitization and output escaping specifically for the 'login_register_login_post' parameter, creating an environment where malicious scripts can be stored and subsequently executed. This dual failure creates a pathway for attackers to inject persistent malicious code that will execute whenever authenticated users interact with compromised pages, making the vulnerability particularly dangerous as it can affect any user who accesses infected content.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to potentially hijack user sessions, steal sensitive information, and manipulate website functionality. The forged request mechanism allows attackers to trick administrators into performing actions without their knowledge, making this attack vector particularly insidious since it relies on social engineering elements combined with technical exploitation. When an administrator clicks on a malicious link or performs an action through a forged request, the stored XSS payload executes within their browser context, potentially leading to complete account compromise and unauthorized access to administrative functions.
Security professionals should note that this vulnerability aligns with CWE-352 for cross-site request forgery and CWE-79 for cross-site scripting, representing a classic combination of web application security flaws that can be exploited through the ATT&CK framework's privilege escalation and persistence techniques. The vulnerability demonstrates the critical importance of implementing proper input validation and output escaping mechanisms, as well as the necessity of using nonce validation for all administrative actions. Organizations should immediately update to patched versions of the login_register plugin, implement additional monitoring for suspicious administrative activities, and consider deploying web application firewalls to detect and block exploitation attempts.
Mitigation strategies should include immediate plugin updates to versions that address the nonce validation and input sanitization issues, implementing comprehensive security auditing of all WordPress plugins, and establishing robust monitoring protocols for administrative actions. The vulnerability highlights the importance of following security best practices such as the principle of least privilege, regular security assessments, and maintaining updated security controls. Organizations should also consider implementing additional layers of defense including content security policies, regular security scanning, and user education to prevent successful exploitation through social engineering components of the attack.