CVE-2026-59544 in Thrive Quiz Builder Plugin
Summary
by MITRE • 07/23/2026
Unauthenticated PHP Object Injection in Thrive Quiz Builder <= 10.9.3.0 versions.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 07/23/2026
This vulnerability represents a critical security flaw in the Thrive Quiz Builder plugin for wordpress systems, where unauthenticated remote code execution can be achieved through PHP object injection attacks. The vulnerability stems from insufficient input validation and sanitization within the plugin's handling of serialized data, allowing attackers to inject malicious PHP objects that are subsequently deserialized without proper authentication checks. This weakness enables arbitrary code execution on affected systems, potentially leading to complete compromise of wordpress installations running vulnerable versions.
The technical implementation of this vulnerability involves the manipulation of serialized PHP objects through specific parameters that are processed by the plugin's backend functionality. Attackers can craft malicious payloads containing serialized object data that, when deserialized by the vulnerable plugin, triggers unintended code execution. This type of attack falls under the category of CWE-502 which specifically addresses deserialization of untrusted data, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter. The flaw exists in the plugin's lack of proper authentication checks before processing serialized input, creating an attack surface that allows any remote user to exploit the vulnerability without requiring valid credentials.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and potential data breaches. An attacker who successfully exploits this vulnerability can gain full administrative control over wordpress installations, enabling them to modify content, steal sensitive data, install backdoors, or use the compromised system as a launch point for further attacks within the network. The unauthenticated nature of the exploit makes it particularly dangerous as it requires no prior access credentials, allowing adversaries to target vulnerable systems indiscriminately. This vulnerability directly violates security principles outlined in OWASP Top Ten 2017 category a08, which addresses insecure deserialization.
Mitigation strategies for this vulnerability require immediate action including updating to the patched version of Thrive Quiz Builder beyond 10.9.3.0, implementing proper input validation and sanitization measures, and applying web application firewalls that can detect and block malicious serialized data attempts. Organizations should also consider implementing network segmentation to limit lateral movement if compromise occurs, while monitoring system logs for signs of exploitation attempts. The remediation process involves not only patching the specific vulnerability but also conducting thorough security assessments of other plugins and themes to identify similar deserialization flaws. Regular security audits focusing on object serialization handling and authentication mechanisms should be implemented to prevent similar vulnerabilities from emerging in the future, aligning with NIST SP 800-53 security controls for system and information integrity.