WordPress website have been hacked

I would like to know what I can do to clean up my installation.

If you have to ask at all, you probably cannot.

Your best bet is to restore a clean backup of your website taken before the hack happened. If you don’t keep your own backups (and you should!) get in touch with your host to see if they can restore your site to an earlier date for you.

Your next best option, if you absolutely have no backups to restore, is to hire a professional to thoroughly clean up the site for you. Most of the WordPress security plugin vendors offer such a clean-up service.

As a last resort, if you absolutely have no backups to restore and cannot pay for a professional to do it for you, kindly carefully follow the guidance in this support article to clean your site as thoroughly as you can: https://ww.wp.xz.cn/support/article/faq-my-site-was-hacked/

Once you’re done (either you restored a backup or cleaned up), follow this guide to harden and secure your site to prevent a future attack: https://ww.wp.xz.cn/support/article/hardening-wordpress/

Good luck!