Security researchers demonstrated vulnerability at EUSecWest security conference in Amsterdam. New Jersey and San Francisco transit systems use contactless fare cards that allow anyone to rewrite the card as needed. The same contactless payment system is used in other US cities, such as Boston, Seattle, Salt Lake City, Chicago and Philadelphia, but the researchers were unable to test these systems as of this writing. The researchers published a modified version of the UltraReset app, called UltraCardTester, to let other users assess whether their transit system is vulnerable to this type of attack.”]