CVE-2021-36845 in YITH Maintenance Mode Plugin
Summary
by MITRE • 09/28/2021
Multiple Authenticated Stored Cross-Site Scripting (XSS) vulnerabilities in YITH Maintenance Mode (WordPress plugin) versions
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability CVE-2021-36845 represents a critical security flaw in the YITH Maintenance Mode WordPress plugin, affecting multiple versions of this popular maintenance mode solution. This authenticated stored cross-site scripting vulnerability arises from insufficient input validation and output sanitization within the plugin's administrative interfaces, creating a pathway for authenticated attackers to inject malicious scripts into the plugin's configuration and management areas. The vulnerability specifically targets the plugin's handling of user-supplied data in stored contexts, where malicious payloads can persist and execute whenever affected pages are loaded by other users with appropriate privileges.
The technical implementation of this flaw stems from the plugin's failure to properly sanitize user input before storing it in the WordPress database and subsequently rendering it in administrative interfaces. When administrators or authorized users access the maintenance mode settings or related management pages, the stored malicious scripts execute within the context of the victim's browser session, potentially enabling attackers to steal session cookies, perform unauthorized actions, or redirect users to malicious sites. This vulnerability operates under the Common Weakness Enumeration classification of CWE-79, which specifically addresses Cross-Site Scripting flaws in web applications. The flaw demonstrates characteristics of CWE-352, indicating a potential for Cross-Site Request Forgery exploitation, as the authenticated nature of the vulnerability allows attackers to leverage existing user privileges for malicious activities.
The operational impact of this vulnerability extends beyond simple script execution, as it creates persistent attack vectors that can compromise the integrity of WordPress administrative interfaces and potentially escalate to full system compromise. Attackers can leverage the stored XSS to manipulate maintenance mode settings, inject malicious code into maintenance pages, or create backdoors for future access. The vulnerability affects not only the plugin's core functionality but also undermines the trust model of WordPress administrative interfaces, potentially allowing attackers to establish persistent presence within the WordPress environment. This type of vulnerability is particularly dangerous in multi-user environments where administrators may have elevated privileges and access to sensitive system configurations. The attack surface is further expanded by the fact that these vulnerabilities can be exploited through various administrative interfaces within the plugin, making detection and remediation more challenging.
Mitigation strategies for CVE-2021-36845 should prioritize immediate plugin updates to versions that address the stored XSS vulnerabilities, as vendors typically release patches that implement proper input sanitization and output encoding. Organizations should also implement network-level monitoring to detect suspicious administrative activities and payload injections, particularly focusing on unusual patterns in plugin configuration changes. Security hardening measures including role-based access controls, regular administrative session monitoring, and implementation of Content Security Policies can provide additional defense layers. The vulnerability aligns with ATT&CK technique T1059.007, which covers Scripting through the execution of malicious scripts in web contexts, and may also map to T1566, representing social engineering vectors that exploit trusted relationships within web applications. Regular security audits of WordPress plugins, implementation of automated vulnerability scanning tools, and maintaining updated security baselines are essential practices to prevent exploitation of similar stored XSS vulnerabilities in other plugins and web applications.