WordPress SiteGround Optimizer, switch_PHP Remote Code Execution

The SiteGround Optimizer plugin <= v5.0.12 for WordPress contains a remote unauthenticated PHP code injection vulnerability which exposes vulnerable webservers to remote code execution. The plugin fails to validate user-controlled data which is inserted directly into an htaccess file. The vulnerability can be used by unauthenticated remote attackers due to the plugin failing to leverage the recommended WordPress REST functionality which ensure requests are being made by authorized users.

Exploitation

Stages

1. A remote unauthenticated attacker submits a crafted REST API request to change the PHP version.
2. The server processes the request and inserts attacker-submitted payload into the htaccess file.
3. The attacker requests the htaccess file directly which is now processed as a PHP file and the injected code is executed.

Prerequisites

The attacker must be able to send crafted packets to the target system. Authentication is not required.

Alert Logic Coverage

Alert Logic® has evaluated its customer base for exposure to the exploit and has developed signatures for mitigating the threat depending on the security service in place.

The Network-Based Intrusion Detection System (IDS) has been updated with the new signatures for this exploit when detected via Alert Logic Threat Manager™. If this signature is detected, an incident is generated in the Alert Logic console.

Recommendations for Mitigation

Upgrade to a non-vulnerable version to mitigate this vulnerability.