If you have Duracells or something equivalent, not likely a problem. But you'll see reports on the web from people that had them leak anyway.
If the batteries are cheapies (or cheapies masquerading as expensive batteries), pull 'em. I had a bunch of Sharper Image batteries leak all over my TV/DVD converters. In the past I've had 9V batteries leak in pedals.
The likelihood is low, but....
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