How to import cookies and bookmarks in Firefox from Opera 15+

In support article Import bookmarks from Google Chrome you can see that it is possible to import cookies and bookmarks from Chrome. Since Opera switched to Webkit from version 15 it turns out they use the same format. To import from Opera to Firefox do the following:

1. Backup your Chrome's cookies and bookmarks, usually located at C:\Users\<your_username>\AppData\Local\Google\Chrome\User Data\Default\ . There are 4 files: Bookmarks, Bookmarks.bak, Cookies and Cookies-journal.
2. Overwrite the previous  4 files with Opera's ones, usually located at C:\Users\<your_username>\AppData\Roaming\Opera Software\Opera Stable\
3. Follow Mozilla procedure above (select cookies and bookmarks to import)
4. Restore Google's cookies.