CVE-2025-54940 is an HTML injection vulnerability identified in the WordPress plugin "Advanced Custom Fields" (ACF) developed by WPEngine, Inc. This vulnerability affects all versions prior to 6.4.3. The flaw allows an attacker with high privileges and requiring user interaction to inject crafted HTML code into the plugin's output. When exploited, this injected HTML can be rendered in the context of the affected WordPress site, potentially allowing the attacker to tamper with page display or manipulate the user interface. The vulnerability is classified as an HTML injection rather than a full code injection or cross-site scripting (XSS), which limits the scope of impact primarily to integrity of displayed content rather than confidentiality or availability. The CVSS v3.0 base score is 3.4 (low severity), reflecting that the attack vector is network-based but requires high privileges (PR:H) and user interaction (UI:R). The scope is changed (S:C), indicating that the vulnerability affects components beyond the initially vulnerable component, but the impact on confidentiality is none (C:N), integrity impact is low (I:L), and availability impact is none (A:N). No known exploits are currently reported in the wild. The vulnerability was published on August 8, 2025, and no official patch links are provided in the data, but upgrading to version 6.4.3 or later is implied as the remediation step. This vulnerability is significant for WordPress sites using the Advanced Custom Fields plugin, especially those with multiple users having elevated privileges who might be tricked into interacting with malicious content. The attack requires user interaction, which reduces the likelihood of automated exploitation but does not eliminate targeted attacks. Given the widespread use of WordPress and the popularity of the ACF plugin for custom content management, this vulnerability could be leveraged to manipulate site content, potentially damaging brand reputation or misleading site visitors.

For European organizations, the impact of CVE-2025-54940 is primarily related to the integrity of web content and user trust. Organizations relying on WordPress sites with the Advanced Custom Fields plugin are at risk of having their page displays tampered with if an attacker can gain high-level access and trick users into interaction. This could lead to misinformation, defacement, or manipulation of displayed data, which can harm brand reputation and user confidence. Although the vulnerability does not directly compromise confidentiality or availability, the integrity impact can indirectly affect business operations, especially for e-commerce, government, or media websites where content accuracy is critical. The requirement for high privileges and user interaction limits the threat to insiders or targeted phishing/social engineering campaigns. European organizations with strict compliance requirements around data integrity and user trust, such as financial institutions, healthcare providers, and public sector entities, should consider this vulnerability a moderate risk. Additionally, the potential for scope change means that the vulnerability could affect multiple components or plugins interacting with ACF, increasing the attack surface. Since no known exploits are reported in the wild, the immediate risk is low, but proactive mitigation is recommended to prevent future exploitation.

1. Upgrade the Advanced Custom Fields plugin to version 6.4.3 or later immediately to apply the official fix addressing this vulnerability. 2. Restrict administrative and high-privilege user access to trusted personnel only, and enforce strong authentication mechanisms such as multi-factor authentication (MFA) to reduce the risk of privilege abuse. 3. Conduct user training and awareness programs to reduce the risk of social engineering attacks that could trick privileged users into interacting with malicious content. 4. Implement Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of injected HTML. 5. Regularly audit and monitor WordPress plugins and themes for updates and vulnerabilities, and maintain an inventory of installed plugins to quickly identify affected components. 6. Use web application firewalls (WAF) with rules tailored to detect and block suspicious HTML injection attempts targeting WordPress plugins. 7. Employ security scanning tools that can detect HTML injection and other content manipulation vulnerabilities in web applications. 8. Review and harden user input sanitization and output encoding practices in custom code interacting with the ACF plugin to minimize injection risks.