Over at hacks.mozilla.org
, Benoit Jacob explains
why cross-domain textures have been disabled for WebGL in Firefox 5. "When a cross-domain image was used as a WebGL texture, the WebGL canvas was "tainted" so that reading from it was no longer possible. Theoretically, that eliminated the concern. But a while ago, a researcher wrote to the public WebGL list with a possible attack that could still allow reading pixels from WebGL textures. The idea was to paint the texture one pixel at a time with a WebGL fragment shader crafted to take an amount of time proportional to its brightness, and then time how long it takes: that would conceivably allow to get an approximation of the original image. Initially this attack seemed difficult to execute practically, but since then further research, including a proof-of-concept has been published which shows the attack to be more realistic than initially expected.
" LWN looked at WebGL vulnerabilities
a few weeks back.
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