Dragging a broken GIF shouldn't call imgContainerGIF::GetFrameAt(0). Bug 329889 was fixed by adding a range check in imgContainerGIF::GetFrameAt, but several comments there (starting with #19) question why it's being called with an out-of-range index.
Dragging and dropping a GIF image from Firefox into Explorer should result in the GIF image being saved in Explorer. Instead, dragging a GIF image from Firefox into Explorer results in a single frame being saved as a BMP image. That's absolutely the wrong behavior, and should be corrected ASAP.
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