The Advanced Country Blocker plugin for WordPress, developed by brstefanovic, suffers from a CWE-1188 vulnerability where a secret bypass key is initialized with a predictable default value during installation. This key is intended to allow administrators to bypass geolocation restrictions but is insecure because it does not require mandatory change upon setup. As a result, any unauthenticated attacker can append this default key to URLs on affected sites to circumvent country-based blocking controls. This authorization bypass undermines the plugin's primary security function, potentially exposing restricted content or services to unauthorized users. The vulnerability affects all plugin versions up to and including 2.3.1. The CVSS 3.1 base score is 5.3, indicating medium severity, with an attack vector over the network, no privileges required, no user interaction, and partial integrity impact but no confidentiality or availability loss. No known exploits have been reported in the wild, and no official patches are currently available. The issue arises from insecure default initialization, a common security anti-pattern, which can be mitigated by forcing secret key changes during installation or using strong random values. Organizations relying on this plugin for geoblocking should assess their exposure and implement compensating controls until a patch is released.

For European organizations, this vulnerability can lead to unauthorized access to content or services that are intended to be restricted by geographic location. This could result in regulatory compliance issues, especially for industries bound by data residency or access control laws such as GDPR or financial regulations. Attackers bypassing geoblocking may also gain access to localized pricing, restricted digital goods, or internal resources, potentially causing financial loss or reputational damage. Since the exploit requires no authentication or user interaction, the risk of automated exploitation is significant once the default key is known. The integrity of access control policies is compromised, though confidentiality and availability remain unaffected. Organizations using this plugin on public-facing websites should consider the risk of unauthorized access and potential abuse, particularly in sectors like e-commerce, media, and government services where geoblocking is critical.

Administrators should immediately verify if the default secret bypass key has been changed from its predictable default value. If not, they should manually update the key to a strong, random value or disable the bypass feature if not needed. Until an official patch is released, consider implementing additional access control layers such as web application firewalls (WAFs) with geolocation rules or IP reputation filtering to supplement the plugin's functionality. Regularly audit access logs for suspicious URL parameters that include the bypass key. Additionally, monitor for plugin updates or security advisories from the vendor and apply patches promptly once available. For new installations, enforce a mandatory secret key change during setup and educate administrators on the risks of default credentials. Consider alternative geoblocking solutions with stronger security postures if the plugin remains unpatched.