CVE-2025-53439 is a vulnerability classified as Improper Control of Filename for Include/Require Statement in PHP programs, specifically affecting the axiomthemes Harper theme versions up to 1.13. This vulnerability enables Remote File Inclusion (RFI), where an attacker can manipulate the filename parameter used in PHP's include or require statements to load arbitrary files from remote or local sources. This occurs due to insufficient validation or sanitization of user-supplied input controlling these file paths. Successful exploitation allows attackers to execute arbitrary PHP code on the target server, potentially leading to full system compromise, data theft, or defacement. Although the vulnerability is labeled as PHP Local File Inclusion in the description, the nature of the flaw and the term 'Remote File Inclusion' imply that remote exploitation is possible if PHP configurations permit it. The vulnerability was reserved in June 2025 and published in December 2025, with no CVSS score assigned and no known exploits reported in the wild yet. The affected product, Harper by axiomthemes, is a PHP-based theme commonly used in content management systems like WordPress, which are prevalent in web hosting environments. The lack of a patch link indicates that a fix may not yet be publicly available, emphasizing the need for immediate mitigation steps by users. The vulnerability's exploitation requires no authentication and can be triggered remotely, increasing its risk profile. The absence of CVSS scoring necessitates a severity assessment based on impact and exploitability factors.

For European organizations, this vulnerability poses a significant risk, especially those operating websites or web applications using the Harper theme on PHP platforms. Exploitation can lead to unauthorized code execution, allowing attackers to implant backdoors, steal sensitive data, or disrupt services. This can result in data breaches affecting personal data protected under GDPR, leading to regulatory penalties and reputational damage. Public-facing web servers are particularly vulnerable, and compromised systems could be leveraged for further attacks such as lateral movement within networks or launching attacks on third parties. The impact extends to availability if attackers deface websites or cause denial of service. Given the widespread use of PHP and WordPress-based themes in Europe, the potential attack surface is considerable. Organizations in sectors like finance, government, healthcare, and e-commerce, which rely heavily on web presence and data confidentiality, face heightened risks. The lack of known exploits currently provides a window for proactive defense, but the ease of exploitation and potential severity necessitate urgent attention.

1. Monitor axiomthemes and official repositories for patches addressing CVE-2025-53439 and apply them immediately upon release. 2. Until patches are available, implement strict input validation and sanitization on all parameters that influence file inclusion paths to prevent injection of malicious filenames. 3. Disable allow_url_include in PHP configurations to prevent remote file inclusion attacks. 4. Employ Web Application Firewalls (WAFs) with rules targeting suspicious include/require patterns and block attempts to include remote files. 5. Conduct code audits of customizations or plugins that interact with the Harper theme to identify and remediate unsafe file inclusion practices. 6. Restrict file permissions on web servers to limit the impact of any successful file inclusion. 7. Regularly back up website data and configurations to enable rapid recovery in case of compromise. 8. Educate development and operations teams about secure coding practices related to file inclusion. 9. Monitor logs for unusual requests or errors related to file inclusion attempts. 10. Consider isolating critical web applications in segmented network zones to reduce lateral movement risks.