I noticed a bug, I'm reporting the details of it.
Create a new post in wordpress 3.5.
control-shift-M : let's embed an image !
Let's embed an image with the Insert From Url feature.
In the alt field, let's write a description containing double quotes.
Finally, let's look at the source code of the post.
The alt="" field will NOT contain the double-quoted text, it stops just before it.
In the previous versions of wordpress, the double quotes were transformed into
" and everything was fine.
Hoping nobody will bash a formerly good feature in the name of accessibility to preserve a thousand persons worldwide maximum, I believe it would be a good idea to revert back to this and process double quotes, changing them into their HTML equivalent :)