Board Thread:Destinypedia Forum/@comment-151.227.181.43-20150321083504/@comment-25916964-20150321230252

Sites such as DESTINYDB have got the item data by 'mining' the game for the data. While its possible that the game stores the info in a csv file, I personally doubt it, and you wouldn't find it anywhere online (unless one of those database sites gives it out, which is unlikely). Its also worth noting that the game data that has been mined may not even be accurate, and will likely contain items that were never intended to make it into the final game.

All that said, Bungie probably has an online database for the website and apps that has all the game item data in it. Not that it would ever be accessible directly. (sadly)