Android app developers should update to Dropbox's latest SDK

IBM's application security research team said Wednesday they had found a way to link their own Dropbox account to an Android app on another person's phone that connects to the storage service. After a successful attack, any data uploaded by the app is delivered to the attacker's Dropbox account.

Dropbox publishes an SDK (software development kit) for linking its service to an app. The flaw, nicknamed "DroppedIn," affected Dropbox SDK versions 1.5.4 through 1.6.1 and was fixed in version 1.62, IBM said in a blog post.

The attack, while serious, isn't easy to carry out. It also won't work if a person has Dropbox's own mobile app installed on their phone, and it won't give an attacker access to the full content of a Dropbox account.

Dropbox said the issue doesn't appear to have been exploited by hackers to access data, and that most of the popular apps using its SDK have been patched.

An attacker must first obtain an access token for a Dropbox-enabled app, which can be done by downloading the app and authorizing it for their own Dropbox account.

The attacker must then lure someone to a website or web page with malicious code. The code grabs from the victim's phone a large cryptographic number, known as a "nonce," that's used as part of the authentication process to link an account. With the access code and the nonce, the attacker can link their own Dropbox account to the victim's Android app.

One way users can tell if they've been attacked is by logging into Dropbox using a PC and checking if there are files that should have been saved by a mobile app using Dropbox that aren't there, IBM wrote. It said there aren't many Android apps that use Dropbox's SDK, but a couple of popular ones do, including Microsoft's Office Mobile and AgileBits' 1Password.

As some affected Android apps may not be updated quickly, the best way to defend against the attack is to download the mobile version of Dropbox, which "makes exploitation impossible," IBM wrote.

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