Simple Custom CSS Plugin

Function "is_customize_preview()" requires WordPress 4.0.0, but your plugin minimum supported version is WordPress 3.0.1.

PHP file should prevent direct access. Add a check like: if ( ! defined( 'ABSPATH' ) ) exit;

load_plugin_textdomain() has been discouraged since WordPress version 4.6. When your plugin is hosted on WordPress.org, you no longer need to manually include this function call for translations under your plugin slug. WordPress will automatically load the translations for you as needed.

Sanitization missing for register_setting().

strip_tags() is discouraged. Use the more comprehensive wp_strip_all_tags() instead.

Library files that are already in the WordPress core are not permitted.

Plugin name "Simple Custom CSS Plugin" is different from the name declared in plugin header "Simple Custom CSS".

Tested up to: 6.7 < 7.0. The "Tested up to" value in your plugin is not set to the current version of WordPress. This means your plugin will not show up in searches, as we require plugins to be compatible and documented as tested up to the most recent version of WordPress.

Missing "License" in Plugin Header. Please update your Plugin Header with a valid GPLv2 (or later) compatible license.

The "Short Description" section is missing. An excerpt was generated from your main plugin description.

One or more tags were ignored. Please limit your plugin to 5 tags.

The plugin name includes a restricted term. Your chosen plugin name - "Simple Custom CSS Plugin" - contains the restricted term "plugin" which cannot be used at all in your plugin name.

Incorrect Stable Tag. It's recommended not to use "Stable Tag: trunk". Your Stable Tag is meant to be the stable version of your plugin and it needs to be exactly the same with the Version in your main plugin file's header. Any mismatch can prevent users from downloading the correct plugin files from WordPress.org.