Yesterday, the entire Internet was talking about how the new Kindle Fire HD was supposed to be incredibly difficult to hack. Turns out, the folks over at XDA Developers are smarter than they thought—one day later, the mystery has already been solved. The exploit is the same one found by sparkym3 in Ice Cream Sandwich, but Amazon must have forgotten to patch it.
As with any root, you can cause some serious damage, or brick your device completely if it's not done properly, so proceed at your own risk.
Before you get started, you'll need to install ADB on your computer. Next, there are a few files you need to download, which you can find here and here. The commands are listed on XDA, and you can watch Reverend Kyle's video below for step-by-step instructions.