The quick release on my shimano sora brakes pops open during braking
On Sora brakes, if adjusted correctly, it should not be possible to force open the wheel release lever by applying the brakes. 

Likely, your brakes are adjusted too tight to allow the lever to close completely. Try releasing a few millimeters of cable, and see if the problem continues. 

If it does, you may have a damaged or defective brake. Take it to your LBS, and have it checked out.