I wouldn't bet on it improving security, personally. If I was a hacker, I can use the User-Agent to know what OS they are using (or close enough). I also know

I wouldn't bet on it improving security, personally. If I was a hacker, I can use the User-Agent to know what OS they are using (or close enough). I also know what browser they are using. I can use this information to create a custom webpage with a white background and similar imagery to look like the native browser form. If the user was unsuspecting, they might not realize it's not a separate window, and think that they were logging into the correct site.