CVE-2021-24756 in WP System Log Plugin
Summary
by MITRE • 12/13/2021
The WP System Log WordPress plugin before 1.0.21 does not sanitise, validate and escape the IP address retrieved from login requests before outputting them in the admin dashboard, which could allow unauthenticated attacker to perform Cross-Site Scripting attacks against admins viewing the logs.
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Analysis
by VulDB Data Team • 12/16/2021
The vulnerability identified as CVE-2021-24756 affects the WP System Log WordPress plugin version 1.0.20 and earlier, representing a critical security flaw that undermines the integrity of the plugin's administrative interface. This issue stems from inadequate input handling mechanisms within the plugin's codebase, specifically in how it processes and displays IP addresses obtained from user login attempts. The vulnerability creates a pathway for malicious actors to inject malicious scripts into the system logs that are subsequently rendered in the WordPress admin dashboard, making it a prime target for cross-site scripting attacks.
The technical flaw manifests in the plugin's failure to properly sanitise, validate, and escape IP address data before displaying it within the administrative interface. This oversight directly violates fundamental security principles outlined in the CWE (Common Weakness Enumeration) catalog under CWE-79, which addresses Cross-Site Scripting vulnerabilities. When the plugin retrieves IP addresses from login requests and incorporates them into HTML output without proper sanitisation, it creates an environment where attacker-controlled input can be executed as script code within the context of an administrator's browser session. The vulnerability is particularly dangerous because it leverages legitimate administrative functionality to deliver malicious payloads, making detection more challenging.
The operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with a potential vector for privilege escalation and persistent access to WordPress administrative interfaces. Administrators who regularly monitor system logs become unwitting participants in the attack execution, as the malicious scripts are rendered when they view the compromised log entries. This scenario aligns with ATT&CK technique T1566.002, which describes social engineering through spearphishing with links, as the attack relies on administrators visiting compromised log entries. The vulnerability also represents a failure in the principle of least privilege, as it allows unauthenticated attackers to compromise authenticated sessions through the manipulation of log data.
Mitigation strategies for CVE-2021-24756 require immediate action to upgrade the WP System Log plugin to version 1.0.21 or later, which contains the necessary patches to address the sanitisation deficiencies. Organizations should implement additional defensive measures including input validation at multiple layers, output encoding for all dynamic content displayed in administrative interfaces, and regular security audits of third-party plugins. The fix addresses the root cause by implementing proper sanitisation routines that ensure IP addresses are properly escaped before being rendered in HTML contexts, thereby preventing script execution. Security teams should also consider implementing web application firewalls with XSS detection capabilities and establish monitoring protocols to identify potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of input validation and output encoding in preventing XSS attacks, particularly in administrative interfaces where privileged access can be gained through exploitation of such flaws.