Predator and CL did not provide any possible suspects.
Using Code Search for the file, "EditingStrategy.cpp" assigning to the concern owner.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/385931fbf1990470dde91e5f12c75db5680193c4

@shend -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

Doesn't seem related to my patch.

Redirecting to yosin@ for triage by the editing team.

Lower to Pri-3 since real world usage of insertHorizontalRule is low.

ClusterFuzz has detected this issue as fixed in range 489151:489186.

Detailed report: https://clusterfuzz.com/testcase?key=5242309351571456

Fuzzer: ifratric-browserfuzzer-v3
Job Type: windows_asan_chrome
Platform Id: windows

Crash Type: Null-dereference READ
Crash Address: 0x00000000
Crash State:
  blink::EditingIgnoresContent
  blink::InsertParagraphSeparatorCommand::DoApply
  blink::CompositeEditCommand::ApplyCommandToComposite
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=windows_asan_chrome&range=435589:435591
Fixed: https://clusterfuzz.com/revisions?job=windows_asan_chrome&range=489151:489186

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5242309351571456


See https://github.com/google/clusterfuzz-tools 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 5242309351571456 is verified as fixed, so closing issue as verified.

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