[Webkit-unassigned] [Bug 242002] New: preventSilentAccess throws NotSupportedError

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Sat Jun 25 08:25:40 PDT 2022


            Bug ID: 242002
           Summary: preventSilentAccess throws NotSupportedError
           Product: WebKit
           Version: Safari 15
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: New Bugs
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: luke at warlow.dev

Safari has "implemented" the `preventSilentAccess` function from the Credential Management API (https://w3c.github.io/webappsec-credential-management/#dom-credentialscontainer-preventsilentaccess).

However, it unconditionally throws a NotSupportedError whenever it's called. This happens on both macOS and iOS from my testing.

The specification doesn't mention this as an expected behaviour and I was surprised to see that the function is implemented but also not implemented, meaning my feature detection looking for the existence of the function fails.

The below code can be pasted into Web Inspector on a secure domain to demonstrate the issue. Both Chromium and Firefox work correctly but Safari fails.

if (navigator.credentials.preventSilentAccess) {
        console.log('preventSilentAccess is implemented');
                .then(() => {
                        console.log('preventSilentAccess succeeded');
    .catch((err) => {
                        console.log('preventSilentAccess failed');


} else {
        console.log('preventSilentAccess is NOT implemented');

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