Some time ago Microsoft dropped support for P3P in IE11 and Edge on Windows 10 (https://msdn.microsoft.com/en-us/library/mt146424(v=vs.85).aspx). Unfortunately P3P remains in use, by default, in IE11 on Windows 7. We have thousands of endpoints that run IE11 on Windows 7 still, yet we get complaints that due to sites not publishing P3P policies, sites are not working.
Chrome, Firefox and likes do not even support P3P, so advice has usually been 'go to a different browser'. Recently we got asked a straight up question: "Can you turn P3P off in the advanced settings for the enterprise please?"
That is a good question. We certainly could, but should we? Microsoft is advicing sites not to public a P3P-policy anymore (see above link), but what exactly are we turning off if we disable P3P in the advanced internet options of IE11?
Does IE11 on Windows 7 have enough defense left if we turn off P3P enterprise wide?
More info on P3P: https://en.wikipedia.org/wiki/P3P