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Bypass Flash Same Origin Policy with Add-On


The same-origin policy is an important concept in the web application security model. The policy permits scripts running on pages originating from the same site.

I found that users using FlashFirebug  are vulnerable to same-origin policy bypass. This Firefox add-ons create a files on the Flash Player Trust directory disallowing same-origin policy.


For this example I will use Facebook Video preview box to trigger this Flash XSS. (Fortunately Faceboook use attachment.fbsbx.com )


By using a Flash XSS plus having FlashFirebug install on the Victim Firefox I can trigger this XSS and bypass Same Origin Policy



I report this to Facebook and this was the response:




And me as a good bounty hunter I report to Adobe:




After doing a bit of looking I found that o-minds.com have a report bug page and here is their response:



 I reply to them and after that I didn't receive a response.


My conclusion:
External Addons can bypass Flash "Same Origin Policy" by adding a files to flash trust directory allowing all Script Access ignoring the Same Origin Policy and this happen without the user knowledge.


Video Poc:






Status:

This bug still works and apparently is not geting fixed soon.









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