[jkarlin]

The Selective Permissions Intervention allows the UA to Disable features for a given permissions policy check.

While small, this is a significant change in the sense that two calls in the same browsing context can have different responses. Notably, even if allowedFeatures says a feature is allowed, it may not be allowed for particular invocations. Any suggestions for additional prose/warnings are welcome.

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[domfarolino]

Hey @clelland, what do you think about this?

[clelland]

In general, I'm a fan of the idea that the user agent should be the ultimate arbiter of whether a feature is allowed or not, and even if the permissions policy structure is set up perfectly by all parties, the UA may have additional knowledge that a feature should not be allowed in a given context.

I like that this phrasing only allows the agent to deny access, and not to arbitrarily grant access as well.

One point about the location of the check; since Define an inherited policy doesn't call through to Is feature enabled, this will mean that it's possible for the user agent to intervene like this and disable a feature in one document, but for the same feature to be enabled in one of its embeds. I don't think we've enabled that situation before. I'm not against it, since again, the browser makes that choice, but it might make it easier for sites which are being blocked to find loopholes.

We should also consider whether the (rather neglected) JS API allowsFeature() and friends should return false in this situation (it's unclear, since that text says "allowed by policy", and doesn't link anywhere useful ☹️)

@annevk for thoughts as well

[scheib]

I'm supportive of the patch, but suggest inlining a note sharing the example of protecting against advertisement scripts. This would help the spec be readable with example and not require reader indirection.

[jkarlin]

@scheib good idea, I've described the example inline.

[jkarlin]

@clelland I added a bit to the allowsFeature API, please take a look.

[ghost]

Please allow my third party app access. I'm not receiving messages

[arichiv]

This LGTM but @clelland was already reviewing so deferring to him