[webkit-dev] Mouse Lock API

Vincent Scheib scheib at chromium.org
Wed Sep 21 13:15:45 PDT 2011

Re: Alexey Proskuryakov's comment:

I'm curious about the following provision in the spec:
> > Mouse events normally considered user gestures (e.g. mousedown, click)
> for security purposes (such as when allowing pop-up windows) should not be
> treated as user gestures when under mouse lock to prevent malicious cross
> origin click redirecting.
> My understanding is that when browser is in control, the primary security
> concern is with making the user believe that they are interacting with a
> different site, and thus stealing confidential data the user types
> (especially passwords). Displaying a pop-up window sounds like a very minor
> issue when malicious code is already in main frame, can draw anything, and
> can control mouse movement. Is there a specific attack scenario where this
> limitation helps?

The concern I was attempting to address is primarily that of click jacking.
E.g. Preventing a malicious top level page from directing unintended clicks
to an iframe with a target site (e.g. a bank).

Upon reflection, perhaps the correct way to limit this is to require the
target element to match the top level origin as well. Then user gestures can
only be delivered to the top level origin.

Re: Mouse lock can be a nuisance.
Yes, it can, but it also is essential for many compelling applications and
user interactions. We believe user-agents can find a balance of providing
that ability and diminishing it's abuse. The example of
Flash's abusable full screen mode is relevant in that I believe the amount
of users enjoying the feature vastly outweigh the amount of nuisance caused.
We'll seek to find the appropriate ease of use and reduction of nuisance,
but in the extreme can fall back onto heavy weight measures such as
installing a web-app or prompting for permission first. The API is designed
to tolerate these methods (asynchronous success/failure).
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