Citi confirms critical bug in iPhone mobile banking app

Saved access codes, other info to hidden file on smartphone and synced computers

Citigroup has urged customers conducting mobile banking from their iPhones to immediately upgrade because a security flaw in the older app secreted account information on the smartphone.

A prominent iPhone security researcher said it would be trivial for someone to access the hidden file if they obtained a lost or stolen phone.

In a letter to customers, the U.S. banking giant said its Citi Mobile app saved banking information -- possibly including account numbers, bill payments and access codes -- in a hidden file on the iPhone.

The same concealed information may have also been saved to the Mac or Windows PC used to sync customers' iPhones via iTunes, Citi acknowledged.

The Wall Street Journal first reported on the bug. Citi later confirmed that it had alerted mobile banking customers and upgraded the software on the App Store.

"During a recent review, we discovered that our U.S. Citi Mobile iPhone banking app was accidentally saving information related to customer accounts in a hidden file on their iPhones," Citi said in a statement Monday. "We have released an update...that corrects the problem. This update deletes any Citi Mobile information that may have been saved to their iPhone or computer, and it eliminates the possibility that this will occur in the future."

Citi's iPhone app was last updated July 19 to version 2.0.3. According to the software's App Store listing, the upgrade to 2.0.3 is mandatory and included both bug fixes and security enhancements.

According to noted iPhone vulnerability researcher Charlie Miller, it would be difficult for a hacker to access the saved file and its data remotely, but easy if they had obtained a lost or stolen phone.

"You'd need an exploit to access it remotely," said Miller, a three-time winner at the annual Pwn2Own hacking challenge and one of three researchers who uncovered the first iPhone vulnerability in July 2007. "But if it was lost, you could easily 'jailbreak' it, which gives you access to all the files."

"Jailbreak" is the term used to describe hacking an iPhone so that the owner can install software not authorized by Apple .

Citi downplayed the threat. "We have no reason to believe that our customers' personal information has been accessed or used inappropriately by anyone," the company said.

"By their statement, I'm guessing that the file isn't encrypted," said Miller, an analyst with Baltimore-based Independent Security Evaluators (ISE) and co-author of The Mac Hacker's Handbook . "If it was encrypted, I would have thought they would have mentioned that."

The biggest threat to users may be due to Citi's iPhone app saving the same information to the Mac or PC used to sync the smartphone, said Miller, noting that vulnerabilities and exploits of personal computers are far more common than those of the iPhone. "That data would be backed up [from the iPhone] to the computer," he said, and thus available.

"But frankly, I'd be more concerned if I lost my wallet than if I lost my iPhone," Miller added.

Citi also noted that other iPhone software, including that used to manage bank-issued credit cards, wasn't affected by the bug.

Join the Good Gear Guide newsletter!

Error: Please check your email address.

Tags citigroupAppleconsumer electronicsMobile Apps and ServicessecuritysmartphonesPhonesMacintosh

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gregg Keizer

Computerworld (US)
Show Comments

Essentials

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >

Budget

Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?