Thanks Massimo. I tried that, but can't really understand the result.

It's definitely not that, Massimo. I've tried Firefox and Edge. Other users of the forum have tried Chrome. It affects all users, not just me.

I've attached a screenshot. I don't use Cloudflare. I had to google it to see what it is 🤔 So I don't think it can be that. Thanks for the suggestion....

Infected? With what?

Thanks. I tried that. Deactivated all plug-ins except wpForo itself, cleared all caches, did the Ctrl +F5 thing. It didn't solve the problem. I guess ...

I have not installed or changed anything for weeks, and this only started a couple of days ago. So, it's not that. I've contacted the hosting service ...