The WooCommerce - PDF Vouchers plugin for WordPress contains an authentication bypass vulnerability (CWE-288) due to insufficient verification of the user during QR code login. This flaw allows unauthenticated attackers who have access to a user ID to log in as that user without proper authentication. The vulnerability affects all versions up to and including 4.9.3. The CVSS 3.1 base score is 7.3, indicating high severity, with network attack vector, low attack complexity, no privileges required, no user interaction, and impacts on confidentiality, integrity, and availability.

An attacker can bypass authentication and gain unauthorized access as any Voucher Vendor user by exploiting the insufficient user verification in the QR code login process. This can lead to unauthorized actions within the plugin's context, potentially compromising sensitive data and disrupting service availability. The vulnerability affects confidentiality, integrity, and availability of the affected WordPress site components related to the plugin.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict access to the affected plugin features and monitor for suspicious activity related to QR code logins. Avoid exposing user IDs publicly to reduce the risk of exploitation.