receiving strange symbols in posts after recent update

Sounds like you have the alternative webp rewrites enabled, can you confirm that?

yes, i have turned it off and it was fixed
can you explain why this is happening?

It’s an encoding issue, and it seems to behave differently on various sites. For our site at work, there was a function I had to disable to make it work, but I’ve seen others where it was necessary to enable that function. Perhaps that is your case. I’ll take a look and see what I can find out.

Try this: https://downloads.www.ads-software.com/plugin/ewww-image-optimizer.zip

You’ll need to deactivate and delete EWWW before you can upload the zip file to the plugin installer.