CVE-2023-5940: 
WordPress vulnerability analysis and mitigation

The WP Not Login Hide (WPNLH) WordPress plugin through version 1.0 contains a stored Cross-Site Scripting (XSS) vulnerability. The plugin fails to properly sanitize and escape some of its settings, which enables high-privilege users like administrators to perform Stored XSS attacks even when the unfiltered_html capability is disabled, such as in multisite setups. This vulnerability was assigned CVE-2023-5940 and was publicly disclosed on November 14, 2023 (WPScan).

The vulnerability exists due to improper input validation in the plugin's settings page. Specifically, the "Warning Message" setting field does not properly sanitize or escape user input. The vulnerability has been assigned a CVSS v3.1 base score of 4.8 (Medium) with the vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N. The issue is classified as CWE-79: Improper Neutralization of Input During Web Page Generation (NVD).

When exploited, this vulnerability allows authenticated administrators to store malicious JavaScript code in the plugin's settings. This stored XSS payload will then be executed whenever any authenticated user visits the settings page. The impact is particularly concerning in multisite WordPress installations where the unfiltered_html capability is typically disabled as a security measure (WPScan).

As of the vulnerability disclosure, there is no known fix available for this issue. Users of the WP Not Login Hide plugin should consider either removing the plugin or implementing additional security controls to restrict access to the plugin's settings page (WPScan).