[Webkit-unassigned] [Bug 163894] New: Remove Unicode case-insensitive matching for usemap=""

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=163894

            Bug ID: 163894
           Summary: Remove Unicode case-insensitive matching for usemap=""
    Classification: Unclassified
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: HTML DOM
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: d at domenic.me
                CC: cdumez at apple.com

In https://github.com/whatwg/html/commit/6acdb2122298d2bb7bb839c0a61b4e1f9b0f9bc9 we changed the HTML spec to remove all of its instances of "compatibility caseless" Unicode case-insensitive matching. There were three:

- <object usemap> matching <map name>
- <img usemap> matching <map name>
- radio button group names

All of these have been replaced with simple case-sensitive matching. WebKit already uses case-sensitive matching for radio button group names; see https://bugs.webkit.org/show_bug.cgi?id=90617#c21. This bug is about the usemap cases.

We believe this change will be low-risk due to Chromium use counter data from the stable channel, which reveals that <0.0001% of pages have a map attribute that matches using ASCII case-insensitive matching, but not using case-sensitive mapping. Furthermore, zero additional matches are triggered by Chrome's Unicode case-insensitive matching. Another reason to believe this is low-risk is that the particular Unicode case-insensitive matching used was highly inconsistent and unreliable across browsers; the spec's "compatibility caseless" was fiction.

More background at https://github.com/whatwg/html/issues/1666 and links contained therein. Web platform tests available at:

- http://w3c-test.org/html/semantics/embedded-content/the-img-element/usemap-casing.html
- http://w3c-test.org/html/semantics/embedded-content/the-object-element/usemap-casing.html

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