CVE-2021-24863 in WP Block and Stop Bad Bots Crawlers and Spiders and Anti Spam Protection Plugin StopBadBots Plugin
Summary
by MITRE • 12/13/2021
The WP Block and Stop Bad Bots Crawlers and Spiders and Anti Spam Protection Plugin StopBadBots WordPress plugin before 6.67 does not sanitise and escape the User Agent before using it in a SQL statement to save it, leading to a SQL injection
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Analysis
by VulDB Data Team • 01/16/2026
The vulnerability identified as CVE-2021-24863 affects the StopBadBots WordPress plugin, specifically versions prior to 6.67, presenting a critical SQL injection risk that stems from inadequate input sanitization practices. This flaw exists within the plugin's handling of user agent strings, which are typically collected by web servers to identify the client software making requests to the server. The plugin's failure to properly sanitize and escape these user agent values before incorporating them into SQL queries creates an exploitable condition that malicious actors can leverage to execute arbitrary SQL commands against the underlying database.
The technical implementation of this vulnerability resides in the plugin's database interaction logic where user agent data is directly concatenated into SQL statements without proper parameterization or escaping mechanisms. When the plugin processes incoming HTTP requests, it captures the user agent string from the HTTP headers and stores this information in the database. However, the plugin does not apply appropriate sanitization routines to remove or escape potentially malicious characters that could alter the SQL command structure. This represents a classic SQL injection vulnerability classified under CWE-89, which specifically addresses improper neutralization of special elements used in SQL commands.
From an operational perspective, this vulnerability poses significant risks to WordPress installations using the affected plugin version. Attackers can exploit this weakness by crafting malicious user agent strings that contain SQL injection payloads, potentially allowing them to extract sensitive data, modify database contents, or even escalate privileges within the affected WordPress environment. The impact extends beyond simple data theft as successful exploitation could lead to complete database compromise, unauthorized access to user accounts, and potential lateral movement within the network infrastructure. The vulnerability affects the integrity and confidentiality of all data stored in the WordPress database that is processed through the StopBadBots plugin's user agent logging functionality.
The security implications of this vulnerability align with tactics and techniques documented in the MITRE ATT&CK framework under the T1071.004 sub-technique for Application Layer Protocol: DNS, as attackers can manipulate HTTP headers to achieve their malicious objectives. Additionally, this vulnerability demonstrates characteristics of T1213.002 for Data from Information Repositories, where attackers can extract sensitive information through database exploitation. Organizations running vulnerable versions of the StopBadBots plugin face potential compromise of their entire WordPress installation, particularly when the plugin is used in conjunction with other security tools that rely on proper input validation.
Mitigation strategies should prioritize immediate patching to version 6.67 or later, which implements proper input sanitization and escaping mechanisms for user agent strings. System administrators should also implement additional protective measures including database query parameterization, web application firewall rules to detect and block suspicious user agent patterns, and monitoring for unusual database access patterns. Network segmentation and least privilege access controls for database connections can further reduce the potential impact of successful exploitation attempts. Regular security audits and vulnerability assessments should be conducted to identify similar input validation flaws in other plugins and themes, as this represents a common weakness in web application security practices.