Update: Add section of DOM skimming to browser extension vuln CS

[canalun]

You're A Rockstar

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This PR fixes issue #1705

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[canalun]

@jmanico
Thank you! :)
Is it better to ask someone to review from me? It requires two approvals. (i'm not so familiar with the review process here)

[szh]

LGTM!

[canalun]

Thanks!