CVE-2025-53454 is a vulnerability classified as CWE-79, indicating an Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting (XSS). This specific vulnerability affects the Rustaurius Ultimate WP Mail plugin, versions up to and including 1.3.8. The flaw allows an attacker to inject malicious scripts that are stored persistently within the application, leading to Stored XSS attacks. Stored XSS occurs when malicious input is saved by the application and later rendered in a web page without proper sanitization or encoding, enabling the execution of arbitrary JavaScript in the context of the victim's browser. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) reveals that the attack can be launched remotely over the network with low attack complexity, requires low privileges, and user interaction is necessary. The scope is changed, meaning the vulnerability affects components beyond the initially vulnerable component. The impact affects confidentiality, integrity, and availability to a limited extent. No known exploits are currently in the wild, and no patches have been linked yet. The vulnerability was reserved in June 2025 and published in September 2025. Ultimate WP Mail is a WordPress plugin, which suggests that the vulnerability affects WordPress sites using this plugin. Stored XSS can lead to session hijacking, defacement, phishing, or malware distribution, depending on the attacker's goals and the victim's privileges.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on WordPress websites that use the Ultimate WP Mail plugin. Stored XSS can compromise user accounts, steal sensitive information, and facilitate further attacks such as privilege escalation or lateral movement within the network. Organizations handling personal data under GDPR may face compliance risks if user data confidentiality is breached. The availability impact is limited but could include website defacement or disruption of mail-related functionalities. Since the vulnerability requires low privileges but user interaction, it may be exploited against employees or customers through crafted links or emails, potentially leading to broader compromise. The medium severity rating suggests that while the vulnerability is not critical, it still poses a meaningful risk that should be addressed promptly to prevent exploitation and reputational damage.

1. Immediate mitigation should include auditing all WordPress sites for the presence of the Ultimate WP Mail plugin and identifying versions up to 1.3.8. 2. If a patch becomes available, apply it promptly. In the absence of an official patch, consider temporarily disabling or removing the plugin to eliminate the attack surface. 3. Implement Web Application Firewall (WAF) rules to detect and block common XSS payloads targeting the affected plugin's input fields. 4. Conduct input validation and output encoding on all user-supplied data rendered by the plugin, if custom modifications are possible. 5. Educate users and administrators about the risks of clicking on suspicious links and the importance of reporting unusual website behavior. 6. Monitor logs for unusual activity that could indicate exploitation attempts, such as unexpected script injections or anomalous user actions. 7. Review and strengthen Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts. 8. Regularly update all WordPress plugins and core installations to minimize exposure to known vulnerabilities.