Yesterday, I had the pleasure of watching on Frikanalen the OWASP talk by Scott Helme titled "What We’ve Learned From Billions of Security Reports". I had not heard of the Content Security Policy standard nor its ability to "call home" when a browser detect a policy breach (I do not follow web page design development much these days), and found the talk very illuminating.
The mechanism allow a web site owner to use HTTP headers to tell visitors web browser which sources (internal and external) are allowed to be used on the web site. Thus it become possible to enforce a "only local content" policy despite web designers urge to fetch programs from random sites on the Internet, like the one enabling the attack reported by Scott Helme earlier this year.
Using CSP seem like an obvious thing for a site admin to implement to take some control over the information leak that occur when external sources are used to render web pages, it is a mystery more sites are not using CSP? It is being standardized under W3C these days, and is supposed by most web browsers
I managed to find a Django middleware for implementing CSP and was happy to discover it was already in Debian. I plan to use it to add CSP support to the Frikanalen web site soon.
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