QGIS » QGIS Application

A recent regression under qgis master (2.3) is causing map items' background color to render white when exporting to image irrespective of the map item background when inserted onto the composer sheet. Steps to reproduce:
1. Create a new project
2. Go to Project Properties and change the background color to a non-white value (e.g. bright pink)
3. Create a new composer
4. Insert a map item, and activate the [x] frame
5. Note the map item's background is (correctly) rendered using the project's background color
6. Export the newly created composer to an image (test.png)
7. Open the resulting image, you'll notice the map item (identifiable with the frame) rendered with a white background

If you manually change the map item background color, the subsequent exports to image will work ok. It might be a MTR-linked regression, but I'm not sure.