Sony acknowledges the light leaks issue. And Ferrell McCollough explains you how to temporarely fix it :)

Goody hair tie around lens bayonet (Courtesy: Ferrell McCollough)

The following is an official Sony answer to Bart (in NJ) request regarding the Sony A7-A7r light leak issue:

Sony is aware of and acknowledges this light leak problem with the A7 and A7r and our engineering department is currently researching a solution. We will release a notice to the owners once a resolution is found.

And if you want to get rid of the problem now follow SAR reader Ferrell McCollough (blog here) advice:

I started with black electrical tape and recently discovered a hair tie (elastics) to be an easy, non-sticky alternative. It’s easy to carry in any camera bag too. Get the Goody variety because it does not have the metal connector and “it will give you the hold you need and the comfort you crave.” They are available at drug stores or online. They are the perfect diameter to stretch around the lens and fit snugly at the joint between the lens and body. Even if you catch them with your fingers while handling the camera they snap back into the groove. Also, it’s easy enough to leave on to cut down on moisture and dust and the possibility that “normal” exposures might be effected by a light leak. The biggest bonus is that it’s NOT unattractive!
http://www.walmart.com/ip/Goody-Ouchless-No-Metal-Hair-Elastics-Little-Black-Dress-27255-36-count

On his blog you can see a simple test that proves how this completely fixes the issue.

Thanks Ferrell McCollough!