The Loginizer WordPress plugin was found to be affected by an Unauthenticated SQL Injection vulnerability found by the security researcher mslavco.
The vulnerability was triggered within the brute force protection functionality, which was enabled by default when the plugin was first installed. When a user attempts to login with an unknown username, the attempt is logged in the backend database, where the username, as well as other parameters, are not properly validated before being placed within the SQL query.
The patch for this issue also included other input sanitisation checks to prevent Cross-Site Scripting (XSS) vulnerabilities.
WordPress issued a forced update to patch this vulnerability. According to the plugin author, this resulted in 89% of sites with the plugin being successfully patched.
Proof of Concept
From the original researcher:
$ sqlmap.py -u http://local.target/wp-login.php --method='POST' --data='log=&pwd=password&wp-submit=Log+In&redirect_to=&testcookie=1' -p log --prefix="', ip = LEFT(UUID(), 8), url = ( TRUE " --suffix=") -- wpdeeply" --dbms mysql --technique=T --time-sec=1 --current-db --current-user