[zamfi]

> When my Macbook Pro is "locked" it flashes an image of the desktop screen just before switching to the login prompt.

This used to happen to me and I was very annoyed. Felt like a major security hole.

But now I get a scrambled image before the login prompt. Are you on the latest macOS?

[rleigh]

I got this just two weeks back, fully up to date 2015 MPB. I was shocked that this could happen; I could even click around on the desktop for a few seconds before it locked up, and I had to hit Esc for the login screen to appear. I didn't even realise it was locked the first time it happened. A very visible reminder about software quality at Apple.

[AHTERIX5000]

I get sometimes scrambled image and sometimes normal desktop before login, it could be rendering something from uninitialized buffer.

[stcredzero]

I also get the scrambled image as well. I am on the latest, last I checked. I generally keep updated.