[CVE-2013-5726] - Tweetbot for iOS and Mac user disclosure/privacy issue

[Guillaume Ross <guillaume () binaryfactory ca>]

- Affected Vendor: http://tapbots.com/
- Affected Software: Tweetbot for Mac, iPad and iPhone
- Affected Version: Mac: 1.3.3 - iPad: 2.8.5 - iPhone: 2.8.5
- Issue Type: Lack of user confirmation leading to Twitter action revealing the user's Twitter identity
- Release Date: November 1, 2013
- Discovered by: Guillaume Ross 
- CVE Identifier: CVE-2013-5726 
- Issue Status: Vendor has published version 3 for iPhone which resolves the issue. Vendor has confirmed the fix is in 
the Mac and iOS V2 codebase and should be released soon.

**Summary**

Tweebot is a Twitter client for Mac and iOS. Separate iOS versions exist for iPhone and iPad.

Tweetbot has a URL Scheme/association on all versions that allows actions to be triggered from within other 
applications. The supported actions can be viewed at http://tapbots.com/blog/development/tweetbot-url-scheme

**Description**

The actions related to following and favoriting do not prompt the user before performing the action. Additionally, 
Safari in iOS warns the user that an application will be launched only when the URL is used directly, but not when the 
URL is used within an inline frame. This makes the attack function without requiring user interaction.

**Impact**

A user browsing the web could click a malicious link or load a page containing a malicious link within an inline frame. 
The user would then favorite a tweet or follow a user account on Twitter. The attacker can use this action to identify 
the user browsing the page, to gather followers or to have the victim follow people they would be embarrassed to be 
associated with.

**Proof of Concept**

        tweetbot:///follow/justinbieber

This URL would have the user follow Justin Bieber. By embedding it in an inline frame, the attack is automated on iOS 
and on Mac.

        <iframe src="tweetbot:///follow/justinbieber"></iframe>

**Response Timeline**

- August 27 2013 - Vendor notified
- August 27 2013 - Vendor acknowledges vulnerability
- October 24 2013 - Tweetbot v3 for iPhone is released and resolves the issue
- October 31 2013 - Vendor confirms the fix is in the V2 and Mac code base and will be released soon
- November 1 2013 - Vulnerability Disclosed

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