Just as passports reveal more than they appear to, so do boarding passes. Sure, your name, seat assignment, seat class, and requisite flight information are there in plain sight, but you may want to think twice before snapping a photo of the paper document and posting it on social media—or throwing it away the moment you get off a flight.

Here’s why: Should someone get access to the barcode printed on airline boarding passes, security bloggers have noted that others may be able to discover more about you, your future travel plans, and potentially, your frequent flier account by using sites like these to break apart the barcode. Once they have your confirmation number number and can log in, subsequent options and information are made available—and once they are, someone could even change your seat, cancel any future flights, and even reset your airline account PIN number. A recent attempt on our end, using a discarded boarding pass, revealed (among other things) the traveler’s name and Passenger Name Record, the code used for finding and tweaking a reservation. Oftentimes, that code is already printed on the boarding pass itself—no barcode needed.

The odds of someone actually doing this are, of course, relatively unlikely, and it’s hard to believe anyone would hack your account only to swap your aisle seat for a middle. Still, it pays to be careful, which means that you should think twice before posting—and save your paper tickets for the shredder.