Understanding the Urna Theme LFI Vulnerability

What is Local File Inclusion (LFI)?

Local File Inclusion is a web application weakness that allows an attacker to coerce an application into loading or exposing files from the server’s filesystem. Unlike remote inclusion, LFI works with files already present on the server. In a WordPress context this can disclose configuration files, credentials, or other secrets and — in certain configurations — lead to code execution.

Urna Theme LFI Details

• Vulnerable Versions: All theme versions ≤ 2.5.7
• Fixed Version: 2.5.8 and later
• Severity: High (CVSS 8.1)
• Access Required: Unauthenticated
• Reported By: Tran Nguyen Bao Khanh
• CVE ID: CVE-2025-54689

The root cause is insufficient sanitisation of user-supplied input used to determine which local files are included. Because no authentication is required, remote attackers can target vulnerable sites directly.

The Impact of This Vulnerability

Why Should You Be Concerned?

Websites using an affected Urna theme are exposed to attacks that can:

• Expose sensitive files such as wp-config.php containing database credentials;
• Reveal user data or internal configuration files;
• In specific server setups, allow unintended execution of PHP code;
• Enable attackers to install backdoors or move laterally across systems.

Magnitude of Risk

With a CVSS score of 8.1 and unauthenticated access, this is a high-risk issue often targeted by automated scanning bots. Each moment a vulnerable site remains unpatched increases the probability of compromise.

How This Vulnerability Works

The vulnerability arises from unsafe use of PHP include/require functions combined with unsanitised input. An attacker can manipulate parameters to traverse directories and reference local files, leading to disclosure or unintended execution of their contents. Typical attack flow:

1. An attacker crafts a request referencing local files (often using directory traversal patterns).
2. The theme processes the input without proper validation and includes the referenced file.
3. Contents of the file are revealed or, in some configurations, executed.
4. Data disclosure or further compromise follows.

For example, successful access to wp-config.php can reveal database credentials in cleartext, which immediately elevates attacker capabilities.

Immediate Actions (Practical, Urgent)

1. Update Urna Theme to Version 2.5.8 or Later

The most effective mitigation is to update the Urna theme to version 2.5.8 or newer without delay. This release addresses the LFI flaw.

2. Audit Your Site for Signs of Compromise

If you believe your site may have been targeted, undertake these checks immediately:

• Review web server access logs for suspicious requests, especially attempts that include directory traversal patterns or unusual query parameters.
• Inspect critical files (wp-config.php, .htaccess, theme and plugin directories) for unauthorised changes.
• Scan for unknown or modified files and suspicious PHP code placed in uploads or theme folders.

3. Temporary Mitigations Until Patching Is Applied

If immediate patching is not possible:

• Harden file permissions so that critical files are not world- or web-server-readable where feasible.
• Disable PHP execution in upload directories.
• Block obvious malicious patterns at the web server or reverse-proxy level (for example, requests containing directory traversal sequences).

How Web Application Firewalls and Virtual Patching Help

A well-configured Web Application Firewall (WAF) or reverse-proxy ruleset can reduce exposure while you patch by intercepting malicious requests that match known LFI patterns (e.g., directory traversal, suspicious include parameters). Virtual patching provides temporary protection by blocking attack vectors rather than fixing the vulnerable code itself. Use such controls as an interim layer, but treat them as a stopgap — not a replacement for applying the official theme update.

Best Practices to Harden WordPress Against Similar Vulnerabilities

Beyond updating, adopt a layered security posture:

• Keep WordPress core, themes, and plugins up to date. Remove unused or unmaintained components.
• Apply least-privilege principles to file system, database, and user accounts.
• Enforce strong authentication and monitor login activity.
• Perform regular security audits and code reviews for custom themes or plugins.
• Maintain frequent, tested backups stored off-site and document recovery procedures.

Detecting Vulnerable Code

Indicators that a theme may be vulnerable to LFI include:

• Use of include/require with file paths derived from query parameters or user input.
• Server error logs showing file inclusion errors or failed attempts to include files.
• URL parameters that accept filenames or relative paths without validation.

Run code reviews and static analysis on theme files to identify unsafe inclusion patterns.

Recovery Steps After Compromise

If compromise is confirmed:

1. Isolate the affected site (take it offline or restrict access) to prevent further damage.
2. Replace core WordPress files, themes, and plugins with clean copies from official sources.
3. Rotate all credentials: WordPress admin, database, FTP/SFTP, hosting control panel, and any API keys.
4. Remove malicious files and backdoors; validate integrity of uploads and theme/plugin directories.
5. Restore from clean backups if available and verified.
6. Consider engaging a professional incident response provider for complex intrusions.

Avoid relying solely on automated malware scanners after an incident; attackers often modify or disable security tooling.

Why Attackers Target Themes

Themes are attractive targets because they frequently:

• Offer many input handling paths and templates;
• Run with the same privileges as WordPress and can access sensitive paths;
• Are often neglected for updates compared to core and plugins.

The Urna LFI is a clear example of the risks posed by third-party components.

Conclusion

The Local File Inclusion vulnerability affecting Urna theme versions up to 2.5.7 is a high-severity issue that requires immediate attention. Update the theme to 2.5.8 or later as a priority. In parallel, audit your site, apply temporary mitigations where necessary, and adopt a layered security approach to reduce future risk.

As security practitioners in Hong Kong, we stress prompt, pragmatic action: patch quickly, verify integrity, and maintain continuous vigilance.