Mihoyo recently fixed a major issue that caused the personal email addresses of every single Genshin Impact player to be publicly accessible information. At the time of writing, the studio has yet to issue an official notice about this.
Usually, Mihoyo updates its in-game noticeboard whenever it makes a change to Genshin Impact. This is accessible via the icon above your inbox, and you will get a notification whenever a new notice is posted. Strangely, Mihoyo hasn't updated players about its most recent adjustment to Genshin Impact, which prevents other players from accessing your personal information - which, up until now, was not just possible, but weirdly easy to do.
The issue and subsequent fix were recently documented on Reddit. It's worth noting that this comes less than a month after it was revealed that you could figure out a player's complete, uncensored phone number just by typing in their username and clicking the "Having problems?" option.
The email address exploit functions in a similar fashion. Admittedly, it has one extra obstacle in place, but this can be quickly overcome with a little bit of easily-obtained know-how.
Essentially, Mihoyo censors your email address when you type your username in, but using in-built browser dev tools allows you to see the full, uncensored version. This isn't high-brow hacking, either - a five-minute YouTube tutorial would probably be enough to teach a person how to use these tools to view the censored characters.
This is no longer an issue, but it's been over two months since Genshin Impact originally launched, meaning that people had access to your personal email address for a pretty long time. Again, Mihoyo hasn't addressed this issue publicly, and issued the fix quietly. It's uncertain if it will post an update notifying players of the potential breach at all.
This whole situation points to how odd it is that a game as big as Genshin Impact still hasn't added two-factor-authentication. To put that in context, Genshin Impact generates an average of $6 million a day and recently won multiple awards, so it's weird to see such a blatant security issue going unnoticed for over two months.