A vulnerability in the software development kit (SDK) that allows third-party Android applications to save data to a Dropbox user's account could have allowed attackers to reroute data to an alternate account, IBM stated in an analysis of the issue published on March 11.
The exfiltration flaw, dubbed DroppedIn by IBM, affects version 1.5.4 and later of the Dropbox SDK, and could be exploited by a malicious Website or an application installed on a victim's smartphone. Exploitation of the vulnerability would unlink a targeted third-party application from the victim's Dropbox account and link the app to the attacker's account. While the attacker would not gain access to files stored on Dropbox's servers, any data that the victim intended to save from the targeted application to their Dropbox account would be copied to the attacker's account instead.
The attack uses a weakness in how the software development kit handled "intents," an Android programming construct that allows linking one application to others.
"The idea is that you bait the end user to go to a rogue site, which messes with the intents on Android and causes a chain of events to occur that switches the storage from being the victim's Dropbox account to the attacker's Dropbox account," Caleb Barlow, vice president of mobile management and security for IBM, told eWEEK.
Dropbox classified the issue as a "minor" security vulnerability, noting that Android users would only be vulnerable if three conditions were true: an app targeted by attackers is installed on the user's device, the Dropbox app is not installed, and the user visited a malicious Web page or installed a malicious application.
"There are no reports or evidence to indicate the vulnerability was ever used to access user data," the company said in a statement sent to eWEEK.
Out of 41 apps tested as part of IBM's initial research into the issue, 76 percent were vulnerable to the attack. Dropbox fixed the issue in December with its SDK for Android version 1.62, but the companies did not immediately disclose the issue to give more time to third-party developers to update their software with the new SDK.
"Mobile app developers need to go into the apps and update them, and their customers need to install the updated app on their phones," Barlow said.
IBM notified Dropbox of the issue in December and commended the company on its response. The cloud storage service responded to the initial report of the flaw within six minutes, confirmed the issue within 24 hours and issued a patch within four days of being notified of the vulnerability. "This was one of the fastest response times the IBM Security team has seen in its long history of vulnerability research," the company said in a statement.
The easiest way for users to protect themselves is to install the Dropbox client on their mobile device. Once the actual Dropbox app is installed, third-party software will use the client to link to the user's Dropbox account, immunizing them against the attack.
"End users should update their apps to the latest versions and install the Dropbox app, which makes exploitation impossible," IBM stated in its analysis.