Popular Mobile Document-Management Apps Put Data at Risk

Dozens of popular file management apps published by a popular operator of an online document management system do not encrypt file transfers to and from user devices, potentially exposing data.

Mobile security firm Wandera, which discovered the issue, described it as impacting 23 of 29 Cometdocs apps on Apple's App Store. Four of the remaining apps did not convert files as claimed, and the other two were not file conversion apps. A random sampling of 31 Android versions of the same apps that Cometdocs has published on Google's official Play store showed them to be leaking private files as well, Wandera said.

"The Cometdocs applications are transferring files without using encryption (via http), providing bad actors the opportunity to cache and retrieve the files," the security vendor said in a report Thursday. The lack of encryption also gives attackers on the same Wi-Fi network as the user an opportunity to access files as they are transmitted to and from Cometdocs servers.

"This is the first time I have seen entire documents sent across the network without strong encryption," says Michael Covington, vice president of product at Wandera. Bad actors and casual eavesdroppers need minimal effort to obtain entire documents being sent to the conversion service, he says. Though Wandera has not performed any random tests of other document management software, it is unlikely that many are leaking full documents like Cometdocs apps, Covington notes.

Thes apps are an example of the risks organizations face when they allow employees to use unmanaged mobile devices and non-vetted apps for work-related purposes. "When users introduce applications and personally-enabled IT setups into the workplace without understanding how they work, it can cause a lot of headaches for IT and security professionals," Covington says.

Wandera said it had notified Cometdocs three times between December 2019 and January 2020 about the issue but has so far not received a response. Cometdocs did not immediately respond to a Dark Reading request for comment.

Cometdocs bills itself as a provider of apps that allow mobile device users to convert PDF documents into Word, Excel, PowerPoint, AutoCAD, HTML, and other formats. The company claims that its apps can also be used to create PDF documents from a variety of other formats, including rarely used ones such as Publisher and XPS. 

Its services include storing documents in the cloud for users so the files can be accessed from anywhere. Cometdocs apps allow users to sign into Gmail, iCloud, DropBox, OneDrive, and other popular file-hosting services and fetch files from there. Or users can manually upload files to the service from their mobile devices.

Cometdocs claims that some 3 million people worldwide currently use its software. The company offers both a free and paid version of its document conversion service.

Covington says that Cometdocs apps appear to be widely used by employees in enterprise settings. "I was honestly surprised to see that Cometdocs is actively used by some of Wandera's largest enterprise customers," Covington notes. "In fact, our researchers first investigated these apps because we saw a data leak originating from one of our customer devices," he says.

One reason for the popularity of Cometdocs' apps could be that many businesses are not equipped with an IT-approved PDF-converter tool. So employees are likely simply going to Apple and Google's mobile app stores and installing something they can use to quickly convert files. "

They assume that such a simple piece of software shouldn’t introduce any risk," Covington says.

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