Prep Plugin for release on WordPress.org

Escape everything that should be escaped.
Add nonce checks where needed.
Sanitize all inputs.
Apply Code style changes across the codebase.
Correct many deprecation notices.
Optimize load order of many filters.

inc/gateways/class-manual-gateway.php

@@ -385,7 +385,7 @@ class Manual_Gateway extends Base_Gateway {
 
 					<h4 class="wu-m-0 <?php echo wu_env_picker('', 'wu-widget-title'); ?>">
 
-						<?php _e('Instructions for Payment', 'wp-multisite-waas'); ?>
+						<?php esc_html_e('Instructions for Payment', 'wp-multisite-waas'); ?>
 
 					</h4>