Within seconds, the app generated a QR code.
It looks just like the ones found on mobile boarding passes but without the branding.
Jaroszewski was then able to use the code at the unmanned scanners that guarded the entrance to the Turkish Airlines CIP lounge in Istanbul.
As the head of Poland's Computer Emergency Response team, Jaroszewski flies 50 to 80 times a year and is no stranger to technology, according to Wired.
He's already used his Android app, which is made up of about 500 lines of Javascript, to access dozens of lounges across Europe.
There have been occasions when the app has failed.
Jaroszewski was keen to stress that he hasn't tried to enter any lounges that he didn't already have access to as a frequent traveller as the legality of the app is not clear.
The app has also never been tested outside Europe, although Jaroszewski presented on the subject on Sunday at a security conference in Las Vegas.
And while many travellers might want to take advantage of the privileges that the app can offer, Jaroszewski is not planning a public release of the technology.
The app could be seen as a security risk since it reveals that the QR reader guarding the entrance to the lounge does not actually check live bookings information with the airline.
However, Chris Goater, a spokesperson for International Air Transport Association (IATA) doesn't think there is a security issue.
He told MailOnline Travel: "Whilst this gentleman and others have found a way to forge a boarding pass, they won't be able to board a flight as airlines will be able to check it against their system.
"There isn't a security implication as you would have to go through security checks anyway.
"You can create the algorithm that generates the ticket but unless you're in the airline's booking system, you won't be in the system."
MailOnline Travel has contacted Turkish Airlines for comment.