Bug 208200

Summary: A SecurityError is thrown when opening indexedDB in an iframe within a same subdomain tree
Product: WebKit Reporter: Benoit F. <benoit.fleuriaud>
Component: Website StorageAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: annevk, bfulgham, cdumez, sihui_liu, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: Safari 13   
Hardware: All   
OS: All   
URL: http://a.indigital.io

Description Benoit F. 2020-02-25 08:52:58 PST 
If you open an IndexedDB connection in an iframe, it throws a SecurityError, that is completely normal if you are in a cross-origin context.

But what if you are in a domain, say "a.example.com", and you embed an iframe with "src" equal to "b.a.example.com".

The standard (https://html.spec.whatwg.org/multipage/origin.html#relaxing-the-same-origin-restriction) states that you can relax the same-origin restriction that would usually by applied by setting the "document.domain" to the same Second-Level Domain (SLD) in both parent and child contexts.

In my example, setting "document.domain" to "example.com" in the top window and the iframe window is legit and should put both in a same-origin context.

Here is a reproduction link (http://a.indigital.io) with a minimalist context. The iframe loads http://b.a.indigital.io, which is a subdomain of the opening window.
Comment 1 Radar WebKit Bug Importer 2022-02-01 11:19:49 PST 
<rdar://problem/88339063>
Comment 2 Anne van Kesteren 2023-09-01 08:33:41 PDT 
That is still cross-origin, though we might change that at some point to use same-site instead. Relaxing the restriction only applies to a select set of features and this is not one of them.

Nevertheless, these days you should not get an exception, but rather partitioned storage.