Krebs on Security wrote a post about the potentially sensitive information contained in the barcodes on boarding passes, particularly the square kind used in mobile boarding passes but really just about any of the more advanced 2D barcodes you’ll also find on paper boarding passes today.
Within this barcode you’ll be able to find your name, frequent flyer number, ticket number, and other potentially sensitive information. I wouldn’t be too concerned because none of this information is enough — by itself — to access your account. You should already have a reasonably good password, and if someone tries to reset your password they should need additional information that isn’t on the boarding pass. However, Krebs provides additional information about how to dig up future reservations and reset PINs for passengers on some airlines (*cough* United *cough*).
Some airlines may also enable people to access and cancel/change a reservation using only a last name and confirmation number. Even if they can’t access the rest of your account, it could ruin an upcoming trip.
The lesson is don’t give people any more information than necessary. There are some sickos out there who enjoy screwing things up for people. If you want to share a picture of a boarding pass online because you got some awesome seat assignment in first class, blur the barcode, cover it up, or do something to make it a little more challenging.
Your barcode also contains a special digit that will be either a “0” or a “3” to indicate if you qualify for PreCheck. Back in the day, PreCheck wasn’t written on the boarding pass, access was granted randomly, and there were fewer security checkpoints. So if you wanted to avoid wasting time in the PreCheck line to find out that you were ineligible that day, scanning your barcode was a great way to hack the system.
Check out the original post if you’re interested in learning more about how to decipher your boarding pass. Krebs also linked to another article that provides more detailed information about what some of the numbers mean.