Another workaround for posting on clearnet, WITHOUT disabling CORS
Disable JavaScript!
This works because the server misconfiguration (missing Access-Control-Allow-Origin header, disallowing 8kun.top to post to sys.8kun.top/post.php) affects the XHR request sent from JavaScript form onsubmit.
When JS is disabled, the form post will fallback to action=” // sys.8kun.top/post.php” and HTML form submissions do not obey Same Origin Policy so the request will go through.
After the post is submitted you will receive a 404 Not Found Error but then can go back to the bread and see your post was received.
How to disable JS depends on your browser but for Safari it can be toggled under the Develop menu (and for convenience you can even bind a keyboard shortcut in System Preferences, Keyboard, Shortcuts, to quickly toggle JS on and off before/after posting)
a more secure alternative to