Suspected CLs:
Findit could not determine the memory tool from the stacktrace. Is it in a new format?

From Code search on the crashed file "EphemeralRange.cpp" suspecting the below.
https://codereview.chromium.org/2251703002
Unable to assign to "iceman@yandex-team.ru" hence assigned to the reviewer.
tkent@: Could you please take a look into this and assign appropriately. 

Route to Editing triage

Lower to Pri-2, since this occurs unusual HTML.

Removing EditIssue view restrictions from ClusterFuzz filed bugs. If you believe that this issue should still be restricted, please reapply the label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

ClusterFuzz has detected this issue as fixed in range 434840:434865.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=5847353561186304

Fuzzer: bj_broddelwerk
Job Type: linux_debug_chrome
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  m_startPosition <= m_endPosition (BODY class="CLASS9 CLASS7"@offsetInAnchor[
] v
  blink::EphemeralRangeTemplate<>::EphemeralRangeTemplate
  blink::firstEphemeralRangeOf
  
Regressed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_chrome&range=404238:404340
Fixed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_chrome&range=434840:434865

Minimized Testcase (2.31 Kb): https://cluster-fuzz.appspot.com/download/AMIfv96yZtk8Io7q-8SItTPFif5u5gfJClBnbyNppRQH9XyH39YjnrgDzLcUmr97t_Qe_jdA6Oij66hNMSNK5DtQCB9pD7Qk_NEPx0e0PnrToJmH25YU2I-qw711PspjqXW1yw5-bzNjq3LcjgVjiWkXwSsgAiNBKg?testcase_id=5847353561186304

See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

ClusterFuzz testcase is verified as fixed, closing issue.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.