CVE-2026-1560 identifies a critical remote code execution (RCE) vulnerability in the Custom Block Builder – Lazy Blocks plugin for WordPress, versions up to and including 4.2.0. The root cause is improper control of code generation (CWE-94) within multiple functions of the 'LazyBlocks_Blocks' class, which allows authenticated users with Contributor-level permissions or higher to inject and execute arbitrary PHP code on the hosting server. This vulnerability is particularly dangerous because it does not require administrative privileges or user interaction, only authenticated access with relatively low privileges. The attack vector is network-based, exploiting the plugin’s handling of custom blocks that can be created or modified by users with Contributor roles. Successful exploitation compromises server confidentiality, integrity, and availability by enabling arbitrary code execution, potentially leading to full site takeover, data theft, or service disruption. The CVSS 3.1 score of 8.8 reflects the ease of exploitation (low attack complexity), the requirement for low privileges (PR:L), and the severe impact on all security properties (C:H/I:H/A:H). Although no public exploits have been reported yet, the widespread use of WordPress and the plugin increases the risk of future exploitation. The absence of a patch at the time of this report necessitates immediate risk mitigation strategies.

For European organizations, this vulnerability poses a significant threat to websites running WordPress with the Custom Block Builder – Lazy Blocks plugin. Exploitation could lead to unauthorized server access, data breaches involving sensitive customer or corporate data, defacement of websites, or use of compromised servers for further attacks such as phishing or malware distribution. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and government, face heightened compliance risks and potential legal consequences. The ability for low-privilege users to execute code increases insider threat risks and complicates access control policies. Additionally, the disruption of web services could impact business continuity and reputation. Given the plugin’s popularity among content creators and agencies, many European SMEs and enterprises could be affected, especially those with collaborative content workflows that grant Contributor access to multiple users.

1. Immediately audit and restrict Contributor-level access to trusted users only, minimizing the number of users who can create or modify custom blocks. 2. Implement strict input validation and sanitization on any user-generated content related to custom blocks, if possible, through custom security plugins or web application firewalls (WAFs). 3. Monitor web server and WordPress logs for unusual activity indicative of code injection attempts, such as unexpected PHP execution or file modifications. 4. Employ network segmentation and least privilege principles to limit the impact of a potential compromise. 5. Regularly back up WordPress sites and databases to enable rapid recovery in case of exploitation. 6. Stay alert for official patches or updates from the plugin vendor and apply them promptly once released. 7. Consider temporarily disabling or removing the Lazy Blocks plugin if Contributor access cannot be sufficiently controlled until a patch is available. 8. Use security plugins that can detect and block suspicious PHP code execution or unauthorized file changes.