On 12/12/13 12:23 PM, Sherief Alaa wrote:

On Thu, Dec 12, 2013 at 7:07 PM, Tom Ritter <tom@ritter.vg

<mailto:tom@ritter.vg>> wrote:
...

    Then a .onion gave me the same canvas popup, which seemed weird.
    Screenshot: http://imgur.com/SYtmONO


I do get the same popup too but I never allow it. Sorry for not
reporting this.

It looks like https://duckduckgo.com/ and http://3g2upl4pq6kufc4m.onion both use JS code that calls canvas.getContext("2d").getImageData(). Search for getImageData in https://duckduckgo.com/d1050.js.  I guess someone is trying to determine if font smoothing is being used by the browser; I can't say why.

But that is what is triggering the prompt.