CVE-2025-66055 is a vulnerability in the Icegram Email Subscribers & Newsletters WordPress plugin, specifically versions up to and including 5.9.10. The issue arises from the unsafe deserialization of untrusted data, which allows an attacker to perform object injection attacks. Deserialization vulnerabilities occur when untrusted input is processed by a program expecting serialized objects, enabling attackers to manipulate the input to inject malicious objects. In this case, the plugin fails to properly validate or sanitize serialized data before deserializing it, leading to potential execution of arbitrary code or other malicious actions. This vulnerability can be exploited remotely without authentication, as the plugin processes data that may be influenced by external users or attackers. While no public exploits or patches are currently available, the nature of the vulnerability suggests a high risk of exploitation, especially in environments where the plugin is actively used to manage email subscriptions and newsletters. The flaw could allow attackers to compromise the confidentiality of subscriber data, alter newsletter content, or disrupt service availability. The vulnerability was published on November 21, 2025, by Patchstack, but lacks a CVSS score, indicating it is newly disclosed and pending further analysis. Organizations relying on this plugin should consider the risk of object injection attacks and prepare to apply patches or mitigations once available.

For European organizations, the impact of CVE-2025-66055 can be significant. The plugin is commonly used in WordPress environments to manage email subscribers and newsletters, which are critical for marketing and communication. Exploitation could lead to unauthorized access to subscriber data, including personal information, violating GDPR and other privacy regulations. Attackers could also inject malicious payloads, leading to website defacement, phishing campaigns, or malware distribution through compromised newsletters. This could damage brand reputation and result in financial losses due to remediation costs and potential regulatory fines. Additionally, disruption of newsletter services can impair business communications and customer engagement. Given the plugin’s integration with WordPress, a widely used CMS in Europe, the attack surface is broad. Organizations with less mature security practices or delayed patching cycles are at higher risk. The absence of known exploits provides a window for proactive defense, but the ease of exploitation and potential for severe consequences necessitate urgent attention.

1. Immediately audit all WordPress installations to identify usage of the Icegram Email Subscribers & Newsletters plugin, especially versions up to 5.9.10. 2. Restrict access to plugin management interfaces to trusted administrators only, using IP whitelisting or VPNs where possible. 3. Disable or deactivate the plugin temporarily if it is not essential or if no patch is available. 4. Monitor web server and application logs for unusual deserialization activity or unexpected serialized data inputs. 5. Implement Web Application Firewall (WAF) rules to detect and block suspicious serialized payloads targeting the plugin. 6. Educate administrators and developers about the risks of unsafe deserialization and encourage secure coding practices. 7. Stay alert for official patches or updates from Icegram and apply them promptly once released. 8. Consider isolating WordPress environments or using containerization to limit the blast radius of potential exploits. 9. Review and enhance backup and incident response plans to quickly recover from potential compromises. 10. Conduct penetration testing focused on deserialization vulnerabilities to identify other potential weaknesses.