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What happens if browser doesn't support X-FRAME-OPTIONS?

Does it render the uri referenced by the iframe OR it doesn't render anything in this case?

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A browser that supports frames but not the X-Frame-Options header (or the corresponding CSP policies) will simply render any frame content, regardless of the origin. It can't implement a security mechanism that it doesn't know about.

X-Frame-Options was implemented by most major browser around 2010 (and only later specified in RFC 7034 in year 2013) - at that time, frames have already long been around. Introducing the header was a reaction to the clickjacking problem that arised due to cross-origin frame embedding which couldn't be fully remediated with framebusting techniques.

  • Thx Aminius, can you please back your answer by a reference? Then I will accept the answer. – Amio.io Mar 11 '17 at 20:07
  • He is right. Why dont you just test it? People dont write documentation in their browsers for nonexistant features. – joe Mar 11 '17 at 20:15
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    @zatziky I'm not sure about what references you're looking for. X-Frame-Options came after the frame technology, so obviously a browser that doesn't know about the header would just ignore it. – Arminius Mar 11 '17 at 20:30
  • @Arminius Thx, it helps me to understand when I read it in other words and other thoughts. – Amio.io Mar 11 '17 at 20:33
  • @zatziky The linked RFC has a little bit of historical background if you're interested. – Arminius Mar 11 '17 at 20:34

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