It is easy to be counterfeited and forged, easily attacked by middlemen, and there are great security risks. At the same time, the browser does not trust the self-signed certificate, so the website with the self-signed certificate will appear "https certificate is not trusted"
Not all https certificates issued by CA institutions are generally supported by all browsers. If the CA organization fails to pass the international WebTrust certification, then many browsers, such as IE browser, don't trust the https certificate issued by it.
When a website applies for purchasing an https certificate, it must choose a CA organization that has passed the international WebTrust certification. At present, among domestic CA, Wotong CA has obtained international and domestic double certification, and its https certificate is globally credible, supporting all browsers.