[webkit-dev] Security advice for linux browsers based on WebKit

Maciej Stachowiak mjs at apple.com
Mon Aug 24 16:16:45 PDT 2009

Hi Adam,

I think it's probably possible to change the default on all platforms  
other than Mac. I do not believe the compatibility issues we're  
concerned about for Mac affect any other port. I think this would be a  
good choice.

For what it's worth, NFS/AFS automounting also affects many Mac OS X  
deployments. We may have to take special measures to detect remote  
mountpoints to mitigate these risks.


On Aug 22, 2009, at 10:05 PM, Adam Barth wrote:

> If you don't use WebKit to build a browser on Linux, you can ignore
> this message.
> By default, WebKit allows local HTML files to inject script into any
> web page.  That means that if you open a local HTML file on your
> machine, it can effective XSS every web site, including the user's
> bank or webmail provider.  To protect against this threat, we have the
> following setting
> Settings::setAllowUniversalAccessFromFileURLs
> which disables this behavior.  For legacy reasons, we default this
> setting to "true," but I'd like to encourage to use the "false"
> setting by default in your browser, especially if your browser runs on
> Linux.
> This issue is particularly important on Linux because many Linux users
> use a network file system, such as AFS or NFS, which maps the entire
> world into the local file system.  For example, if I made my home
> directly world-readable, it's quite likely that I would be able to
> control this URL on your user's machines:
> file:///afs/cs.stanford.edu/u/abarth
> If you don't override WebKit's default setting, I might be able to
> leverage this ability to read your user's email or transact on your
> user's bank accounts.
> Of course, even with the "false" setting, I might still be able to
> read the contents of your user's /etc/passwd file or other sensitive
> information in your user's file system.  Over time, I hope we can
> further restrict the privileges granted to file URLs.  However,
> removing universal access is a necessary first step.
> Please let me know if you have any questions.
> Adam
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