Italicized in Chrome, Bold in Firefox

I don’t know what happened but when I use Chrome, the normal texts are italicized:

when I use Firefox, the normal texts are bold:

(Even when I’m making this post, since I’m using Chrome, the text I’m typing is currently in italics.)
What happened and how can I fixed this?
Answer #1
Check Firefox tools – option content .
or reinstall firefox.
Answer #2
How about google chrome? Should I reinstall it too?