Thanks Yoav, responses inline! > So the upper bound for potential breakage is 0.04%?
I believe this is a reasonable estimate, although I think it assumes that page loads are evenly distributed across UMA-enabled clients and I'm not sure whether that's the case > Are there ways to tighten it? (e.g. through manual sampling or use-counter changes) Regarding manual sampling, we could investigate by looking at the domains associated with an existing use counter for this: https://chromestatus.com/metrics/feature/timeline/popularity/4169. I suspect that the majority of cases we would encounter would be the cross-origin fetches that are already blocked, though, matching the high percentage of these in our metrics. Making use-counter changes is certainly an option if the consensus is that the upper bound still seems too risky (even given that Firefox and Safari currently ship this behavior and given the proposed mitigations). Alternatively, we could enable this functionality in Chrome Canary, Dev, and Beta for a few weeks and see if we get any bug reports. WDYT? > What does breakage look like? What do these sites see in Safari today? Blocking cross-partition fetches / subframe navigations is implemented in both Firefox and Safari today, so for both of those browsers the fetch / navigation fails and DevTools shows a warning message. The partitioning scheme is slightly different across browsers - Safari partitions by top-level origin and Firefox partitions by top-level site + whether there was a cross-site frame in the frame tree, and the Chrome behavior will match the Firefox behavior for this. -Andrew On Sun, Feb 9, 2025 at 11:21 PM Yoav Weiss (@Shopify) < yoavwe...@chromium.org> wrote: > Thanks for the compat analysis! > > > On Fri, Feb 7, 2025 at 6:48 PM Andrew Williams <awil...@chromium.org> > wrote: > >> Hey everyone, >> >> From looking at use counters for these cases, cross-top-level-site Blob >> URL navigations that would have noopener set as part of this change are >> seen on 0.0004% of page loads. Note that this is calculated from data from >> pre-stable channels and could change when looking at Stable data, but it >> seems unlikely to change by orders of magnitude. >> >> For cross-partition Blob URL fetches, these occur on 0.21% of page loads, >> but from digging into this more and from looking at UMA data, at least 83% >> of those cross-partition Blob URL fetches are guaranteed to be blocked >> today because they are also cross-origin, and only ~21% of UMA-enabled >> clients reported at least one cross-partition fetch that wasn't guaranteed >> to be blocked. It's likely that the remaining 17% of cross-partition Blob >> URL fetches are cross-origin as well and would already be blocked, but our >> current use counter / metrics implementations don't provide a way to gauge >> this. More details on this analysis can be found at: >> https://crbug.com/387655548#comment2 >> > > So the upper bound for potential breakage is 0.04%? > If so, that's too high for comfort from my perspective. > Are there ways to tighten it? (e.g. through manual sampling or use-counter > changes) > What does breakage look like? What do these sites see in Safari today? > > >> Overall I think the use counter metrics + supporting UMA data support >> moving forward with this change, as does the fact that Firefox and Safari >> have already implemented similar functionality. If there is breakage as a >> result of this, we do have an enterprise policy to disable it, we'll have a >> chrome://flags entry so that users can disable it, and we'll have a Finch >> feature flag as a killswitch for any cases of widespread, significant >> breakage. >> >> Regarding formal signals from Gecko and Webkit, we opened one from Gecko >> but haven't heard anything: >> https://github.com/mozilla/standards-positions/issues/1151. For WebKit, >> we reached out regarding whether we should open one and they mentioned they >> didn't think we needed to, given that we plan to implement what the >> functionality they have already, just using sites instead of origins. >> >> -Andrew >> >> On Thu, Dec 12, 2024 at 12:35 PM Andrew Williams <awil...@chromium.org> >> wrote: >> >>> Thanks Domenic, we've landed a change to remove .tentative from the test >>> file names: >>> https://chromium-review.googlesource.com/c/chromium/src/+/5967596 >>> >>> Gregg, IIUC "top-level->iframe(blob-from-top-level)" means the top-level >>> creates a blob URL and then creates an iframe where the src is that blob >>> URL. Similarly, "top-level->iframe(3rd-party)->iframe(blob-from-3rd-party)" >>> means that the 3rd-party iframe creates a blob URL and then creates an >>> iframe where the src is that blob URL. Neither of those cases will be >>> affected by this change. >>> >>> Daniel, thanks for the feedback. We will collect use counts on this and >>> report back once the data is available (should be around mid-February). In >>> the meantime, we will request formal signals from Gecko and WebKit as you >>> recommended. >>> >>> On the topic of alignment across browsers, the I2S mentions that all >>> navigations will remain partitioned only by frame origin, but I learned >>> recently that Safari and Firefox partition subframe navigations (like using >>> a blob URL as the src of an iframe) by storage key / the top-level as well >>> (and this is what was originally proposed in >>> https://github.com/w3c/FileAPI/issues/153). It's only top-level >>> navigations that remain partitioned only by frame origin. Our >>> implementation will follow suit. I'll update the Chrome Status description >>> accordingly. >>> >>> -Andrew >>> >>> On Wed, Dec 11, 2024 at 11:38 AM Daniel Bratell <bratel...@gmail.com> >>> wrote: >>> >>>> After discussing this on the API OWNER meeting I have a few questions >>>> and suggestions. >>>> >>>> My main concern is that we don't have full understanding of the >>>> compatibility risk. We believe this is rare, but do we have any hard data >>>> to confirm that? If not, would it be possible to add a targetted use >>>> counter that counts the cases where a page tries to use a broken blob? >>>> >>>> I think you should also request formal signals from Gecko and WebKit >>>> since this is not exactly what they have done. It seems from what you write >>>> that we're getting something very slightly different (which also means that >>>> what seems to work for them might still break in Chromium). >>>> >>>> /Daniel >>>> On 2024-12-10 03:29, Domenic Denicola wrote: >>>> >>>> LGTM1, nice work on all the spec changes here! >>>> >>>> Please send a web platform tests PR to remove the .tentative.html from >>>> the test filenames. >>>> >>>> On Tue, Dec 10, 2024 at 10:49 AM Gregg Tavares <g...@chromium.org> >>>> wrote: >>>> >>>>> Sorry if I'm not up on all of the latest. I have several sites that >>>>> use blobs in iframes to implement user code execution (think >>>>> JSFiddle/Codepen). Do I need to be worried? >>>>> >>>>> Some use top-level->iframe(blob-from-top-level). Others use >>>>> top-level->iframe(3rd-party)->iframe(blob-from-3rd-party) >>>>> >>>>> They all currently work across browsers so I'm guessing I don't need >>>>> to worry if Firefox and Safari already implement this. >>>>> >>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to blink-dev+unsubscr...@chromium.org. >>>> To view this discussion visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra8377qyjY1fv99%2BnDhJZjWN8j9CdGFLsuwrZVyHJYwUMg%40mail.gmail.com >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra8377qyjY1fv99%2BnDhJZjWN8j9CdGFLsuwrZVyHJYwUMg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to blink-dev+unsubscr...@chromium.org. >> To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAEa0%2BkVgqdOa3MKSoUqvfdH3thYyqm3pM9Paib2frzALG3BhrQ%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAEa0%2BkVgqdOa3MKSoUqvfdH3thYyqm3pM9Paib2frzALG3BhrQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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