on Fiction University:

Not everything you know about your story belongs in your novel.

People tend to think infodumps are the bane of science fiction and fantasy writers, but they happen to everyone. Mystery writers dump how and why characters wound up in places they shouldn’t be in, romance writers share the tragic backstories of the love interests, historical writers elaborate on the history (though their readers probably enjoy their infodumps), and mainstream writers share way too much information about the people and places in their story.

We all do it, and I actually don’t mind infodumps on a first draft. It’s a useful way to get the history and backgrounds straight in my head as I write, but they’ve got to go during draft two.