CVE-2021-4419 in WP-Backgrounds Lite Plugin
Summary
by MITRE • 07/12/2023
The WP-Backgrounds Lite plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 2.3. This is due to missing or incorrect nonce validation on the ino_save_data() function. This makes it possible for unauthenticated attackers to save meta data via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.
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Analysis
by VulDB Data Team • 07/12/2023
The WP-Backgrounds Lite plugin for WordPress represents a widely used tool for managing website backgrounds, yet it contained a critical cross-site request forgery vulnerability that exposed countless websites to potential compromise. This vulnerability existed in versions up to and including 2.3, affecting numerous WordPress installations that relied on the plugin for background customization features. The flaw specifically targeted the ino_save_data() function, which serves as the primary mechanism for saving background-related metadata within the plugin's functionality. The vulnerability stems from the absence of proper nonce validation, a fundamental security measure that ensures requests originate from legitimate sources within the WordPress ecosystem.
The technical implementation of this vulnerability allows unauthenticated attackers to craft malicious requests that appear to come from legitimate administrative users. When an administrator visits a compromised page or clicks on a malicious link, the forged request can execute the ino_save_data() function without proper authentication verification. This creates a scenario where attackers can manipulate background settings, potentially injecting malicious code or altering website configurations that affect user experience and site functionality. The attack vector relies heavily on social engineering techniques, as attackers must deceive administrators into performing actions that trigger the malicious request execution. This makes the vulnerability particularly dangerous because it leverages the trust relationship between the administrator and the website rather than exploiting direct system weaknesses.
The operational impact of this vulnerability extends beyond simple background modifications, as it provides attackers with a foothold for more extensive compromise of WordPress installations. Once an attacker successfully exploits the CSRF vulnerability, they can manipulate the plugin's metadata storage, potentially leading to persistent changes that affect multiple site visitors. The vulnerability also demonstrates a broader pattern of security oversight in WordPress plugin development, where essential authentication mechanisms are either omitted or improperly implemented. This type of vulnerability directly violates security best practices outlined in the OWASP Top Ten and aligns with CWE-352, which specifically addresses Cross-Site Request Forgery weaknesses in web applications. The attack surface is particularly concerning given that WordPress plugins often have elevated privileges and can modify core site functionality.
Mitigation strategies for this vulnerability require immediate action from affected site administrators, including updating to the patched version of the WP-Backgrounds Lite plugin where available. Security professionals should implement additional layers of protection such as web application firewalls that can detect and block suspicious request patterns, particularly those involving the ino_save_data() endpoint. Network monitoring should be enhanced to detect unusual administrative activities or unauthorized metadata modifications that might indicate exploitation attempts. The incident highlights the importance of proper nonce implementation as outlined in the WordPress Plugin Developer Handbook and aligns with ATT&CK technique T1059, which covers command and scripting interpreters. Organizations should also conduct comprehensive security audits of their installed plugins to identify similar vulnerabilities, as this particular flaw represents a common pattern in plugin security implementations. Regular security updates and patch management processes become essential defensive measures against such vulnerabilities that exploit fundamental authentication mechanisms.