CVE-2026-96562 in Broken Link Checker Plugin
Summary
by MITRE • 10/16/2026
The The Broken Link Checker plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 2.4.14.1. This is due to the software allowing users to execute an action that does not properly validate a value before running do_shortcode. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes. Exploitation requires that a submitted comment containing the shortcode payload in an href or src attribute is approved through the site's normal comment moderation workflow; once approved, the shortcode is executed automatically via WP-Cron without any further attacker interaction.
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Analysis
by VulDB Data Team • 10/16/2026
The Broken Link Checker plugin for WordPress contains a critical vulnerability affecting all versions up to and including 2.4.14.1 that allows unauthenticated attackers to execute arbitrary shortcodes within the context of the target website. This flaw stems from an improper validation mechanism where user-supplied input is processed without sufficient sanitization before being passed to the do_shortcode function. The specific vector involves submitting a comment containing malicious shortcode payloads embedded within href or src attributes. Because the plugin processes these comments, it inadvertently treats them as executable code rather than static text, leading to unintended command execution on the server side.
The exploitation of this vulnerability relies heavily on the WordPress comment moderation workflow. An attacker does not need valid credentials or administrative access; instead, they simply submit a crafted comment with the malicious shortcode payload. The critical step in the attack chain is that this comment must be approved by a site administrator through the standard moderation process. Once the comment is marked as approved and published on the front end of the website, it becomes part of the page content. This design choice means that while initial access requires minimal privileges (just the ability to post comments), the actual impact is realized only after administrative approval, which can be a significant hurdle but also makes detection difficult until execution occurs.
The operational impact of this vulnerability is severe because WordPress shortcodes are powerful tools capable of executing complex PHP functions and accessing sensitive data or system resources depending on their implementation. By forcing the execution of arbitrary shortcodes, an attacker can potentially achieve remote code execution, escalate privileges to administrative levels if vulnerable plugins are present, exfiltrate database contents, deface the website, or install persistent backdoors such as web shells. The use of WP-Cron further complicates mitigation because the shortcode execution is triggered automatically when WordPress cron jobs run, meaning the attack payload executes without requiring immediate user interaction with the specific page after approval. This automation ensures that once a comment is approved, the malicious code will eventually run during routine maintenance tasks or scheduled events managed by WP-Cron.
From a technical classification perspective, this vulnerability aligns with CWE-94 Improper Control of Generation of Code (Code Injection) and specifically relates to CWE-78 Improper Neutralization of Special Elements used in an OS Command if the shortcodes lead to system-level commands. In terms of the MITRE ATT&CK framework for Enterprise, this behavior maps to T1059 Command and Scripting Interpreter, as it involves executing code via a scripting environment inherent to WordPress. It also touches upon T1136 Create Account since attackers often use comment sections or user registration forms to establish initial footholds before leveraging such execution flaws. The lack of input validation on data that is subsequently rendered in an executable context represents a fundamental failure in secure coding practices regarding output encoding and function parameter sanitization.
Mitigation strategies must address both immediate remediation and long-term security hygiene. The primary and most effective solution is to upgrade the Broken Link Checker plugin to version 2.4.15 or later, where this validation flaw has been patched by developers who implemented stricter input filtering before passing data to do_shortcode. For sites unable to update immediately due to compatibility concerns, administrators should disable comment moderation approval for untrusted users or restrict commenting capabilities entirely if not required. Additionally, implementing a Web Application Firewall can help detect and block requests containing known malicious shortcode patterns in comment submissions. Regular audits of installed plugins are essential to ensure that all components adhere to current security standards and do not expose the application layer to injection-based attacks. Monitoring WP-Cron logs for unusual activity or unexpected PHP errors may also provide early indicators of exploitation attempts, allowing administrators to respond before significant damage occurs.