Steal Yahoo Crumb By Combining Missing-Iframe and Noscript Tag

a couple of days ago

Few months ago, while testing some html, I was noticed by a straight behaviour in Firefox.

If you disable javascript and open a website, the content inside <noscript> tag does not render as html.

Yahoo use crumb as a token to validated that the request is valid and trusted. You can fetch personal data with this value.

Luckily, I knew that Yahoo put crumb (a type of user token) as a parameter in logout url in <noscript> tag.

What’s next ? Find some Yahoo domain that missing Iframe header, and luckily (again), I got some domain after few minutes.

By combining my lucky, this code help me do the rest

<iframe id='inneriframe' scrolling=no src="https://safety.yahoo.com/poll/entry." sandbox="" />

So ? Time to get some bounty !!  (awarded $x00)

Yeye !

POC video here.

If you are interest, here is another article related to this bug 😀

https://medium.com/@0xHyde/yahoo-two-xssi-vulnerabilities-chained-to-steal-user-information-750-bounty-e9bc6a41a40a

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A&C

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