Light leak?

A friend of mine just got her film scans back and she noticed this weird lightleak on her images. She has the canon f1.

What would be causing it? How can she fix it?
Thank you for your help!

This is the worst of the roll. On others it is just a spot of light like a reflection in a window.

It's white with no yellow or red rim, so if it's a light leak, it would be at the front of the camera. The first thing that comes to mind is a punctured shutter curtain. I'm not too familiar with the F1; I assume it has a curtain shutter, yes? I'd inspect it; there's probably a tiny hole close to the lower right corner when looking through the (open) back of the camera.

You do not say which Canon F-1 model we are talking about. Both the earlier F-1 and F-1n and the later New F-1 have horizontally traveling titanium shutter curtains. It is very rare to have a pinhole in one of these curtains. That's something seen with cloth curtains. If a shutter curtains has a pinhole, the light leak appears in the same spot every time. The New F-1 does have one quirk relating to light leaks. All of the caps on the bottom must be in place to prevent light from leaking in. If caps are missing then light leaks may appear in different places, depending on the angle the light rays enter.