CVE-2021-24909 in ACF Photo Gallery Field Plugin
Summary
by MITRE • 01/17/2022
The ACF Photo Gallery Field WordPress plugin before 1.7.5 does not sanitise and escape the post parameter in the includes/acf_photo_gallery_metabox_edit.php file before outputing back in an attribute, leading to a Reflected Cross-Site Scripting issue
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Analysis
by VulDB Data Team • 01/19/2022
The vulnerability identified as CVE-2021-24909 affects the ACF Photo Gallery Field WordPress plugin, specifically versions prior to 1.7.5, creating a reflected cross-site scripting weakness that poses significant security risks to WordPress installations. This issue stems from inadequate input validation and output escaping mechanisms within the plugin's codebase, particularly in the includes/acf_photo_gallery_metabox_edit.php file where user-supplied data is processed without proper sanitization before being rendered back to users in HTML attributes.
The technical flaw manifests when the plugin fails to properly sanitize the post parameter received from user input before incorporating it into HTML output attributes. This oversight creates an environment where malicious actors can inject malicious scripts that will execute in the context of other users' browsers when they view the affected pages. The vulnerability is classified as reflected XSS under CWE-79, which occurs when user input is immediately reflected back in the application's response without adequate validation or encoding. The specific implementation flaw lies in the plugin's failure to apply proper HTML escaping techniques to prevent script execution in attribute contexts.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and redirection to malicious websites. When exploited, the reflected XSS could allow an attacker to steal cookies, modify page content, or even redirect users to phishing sites that appear legitimate to the victim. The vulnerability affects WordPress users who have the affected plugin installed, potentially compromising the security of entire websites if attackers can leverage this weakness to gain unauthorized access or manipulate content. The reflected nature of the vulnerability means that attackers need only convince victims to click on a malicious link containing the exploit payload, making it particularly dangerous in social engineering scenarios.
Mitigation strategies for this vulnerability include immediate upgrading to version 1.7.5 or later of the ACF Photo Gallery Field plugin, which contains the necessary patches to address the sanitization and escaping issues. Administrators should also implement additional security measures such as regular security audits of installed plugins, monitoring for suspicious user activity, and implementing Content Security Policy headers to limit the impact of potential XSS attacks. The vulnerability aligns with ATT&CK technique T1566.001 for initial access through malicious links and T1546.001 for persistence mechanisms that could be employed after exploitation. Organizations should also consider implementing web application firewalls and input validation rules to provide additional layers of protection against similar reflected XSS vulnerabilities in other components of their WordPress installations.