Specifically, the plan is to do the following: 1) Make the property non-enumerable (needs some codegen changes). 2) Add a counter for how often the window resolve hook is run for a property named "content". This will also trap sets of "content" and "var content", so might not turn out to be useful unless it's very very low; it's basically an upper bound on "content" usage. 3) Add a counter for how often the getter is called from untrusted code.

Since we need this for removing it (bug 1400140), I guess P2 is appropriate.

Actually, I don't think #2 is at all useful, because we would trigger that resolve hook when setting up the window object itself... I'm going to do the other pieces, though. I did try to poke at GitHub searching for "content in window" (yes, I checked that it finds other detection code using a similar search, e.g. "scrollX in window"), and don't obviously see anyone using it for sniffing.

MozReview-Commit-ID: 9F0ZNverS63

MozReview-Commit-ID: LQkEkdG8wKf

MozReview-Commit-ID: LFMK7lxs46Z

Comment on attachment 8908949 [details] [diff] [review] part 3. Add a use counter when the window.content getter is called from untrusted code Review of attachment 8908949 [details] [diff] [review]: ----------------------------------------------------------------- This patch adds a warning and, as far as I can tell, no usage counter, so the commit message is a bit confusing :-/

Comment on attachment 8908949 [details] [diff] [review] part 3. Add a use counter when the window.content getter is called from untrusted code > This patch adds a warning and, as far as I can tell, no usage counter Everything in nsDeprecatedOperationList.h automatically gets a usage counter. See http://searchfox.org/mozilla-central/rev/6769c4c331c85870ac3e7bf61968db98c16e4777/dom/base/UseCounter.h#29-32 and http://searchfox.org/mozilla-central/rev/6769c4c331c85870ac3e7bf61968db98c16e4777/dom/base/nsDocument.cpp#10543-10546 and so forth.

Pushed by bzbarsky@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/6ecbba14b2f3 part 1. Add infrastructure for marking WebIDL interface members as non-enumerable. r=qdot https://hg.mozilla.org/integration/mozilla-inbound/rev/5bc10c68bbf7 part 2. Make window.content non-enumerable. r=mystor https://hg.mozilla.org/integration/mozilla-inbound/rev/df23db5d453e part 3. Add a use counter when the window.content getter is called from untrusted code. r=mystor

https://hg.mozilla.org/mozilla-central/rev/6ecbba14b2f3 https://hg.mozilla.org/mozilla-central/rev/5bc10c68bbf7 https://hg.mozilla.org/mozilla-central/rev/df23db5d453e