LimitLoginAttempts.php in the limit-login-attempts-reloaded plugin before 2.17.4 for WordPress allows a bypass of (per IP address) rate limits because the X-Forwarded-For header can be forged. When the plugin is configured to accept an arbitrary header for the client source IP address, a malicious user is not limited to perform a brute force attack, because the client IP header accepts any arbitrary string. When randomizing the header input, the login count does not ever reach the maximum allowed retries.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-35590
• https://n4nj0.github.io/advisories/wordpress-plugin-limit-login-attempts-reloaded/
• https://wordpress.org/plugins/limit-login-attempts-reloaded/#developers