Test at https://github.com/w3c/web-platform-tests/pull/8290 which causes Safari to crash. The spec was unclear on what to do; see https://github.com/whatwg/html/issues/3217 (where Mozilla seems to have encountered a similar crash). The spec is now being clarified in https://github.com/whatwg/html/pull/3235.
Could you please attach a crash log?
(In reply to Alexey Proskuryakov from comment #1) > Could you please attach a crash log? See bug 187805 comment 0 *** This bug has been marked as a duplicate of bug 187805 ***