As they received their first shipment of fixed 5D Mark IIIs the crew over at LensRentals.com couldn't help but take a quick peak to see how Canon solved the light leak issue. They were not at all surprised by their findings but you may be. Apparently all it took was a little bit of tape.
"We got our first “new” 5D III cameras today, the ones with the light leak fixed. You know me, I thought perhaps it would be a good idea to take one apart and see what was different. I had photos from the ‘prefixed’ 5D IIIs from a previous post, so comparison would be easy.
Let me say it here first: I knew this was going to be the fix since the first time I took one apart: Canon has this very cool black tape they used to cover circuit boards (I’m assuming either water resistance or electrical shielding or both) and I figured they’d just slap another piece over (or under, depending on your point of view) the top LCD light. Which is exactly what they did. Yes, I’m making fun, but it’s a perfectly good solution and it works flawlessly."