wordpress-website-lifecycle/mu-plugins/_core-http-query-string-errors.php

<?php

/*
 * Plugin Name: Log not WordPress friendly URL query strings
 * Plugin URI: https://github.com/szepeviktor/wordpress-website-lifecycle
 */

add_action(
    'parse_request',
    static function () {
        if (empty($_SERVER['QUERY_STRING'])) {
            return;
        }

        if (strpos($_SERVER['QUERY_STRING'], '+') !== false) {
            error_log(sprintf(
                'Non-WordPress query string: plus_encoded_whitespace ("%s")',
                $_SERVER['QUERY_STRING']
            ));
            return;
        }

        if (strpos($_SERVER['QUERY_STRING'], '*') !== false) {
            error_log(sprintf(
                'Non-WordPress query string: not_encoded_asterisk ("%s")',
                $_SERVER['QUERY_STRING']
            ));
            return;
        }

        if (preg_match('/%[[:xdigit:]]?[a-f]/', $_SERVER['QUERY_STRING']) === 1) {
            error_log(sprintf(
                'Non-WordPress query string: lower_case_hexadecimal_digit ("%s")',
                $_SERVER['QUERY_STRING']
            ));
            return;
        }
    },
    0,
    0
);