Predator and CL could not provide any possible suspects.
Using the code search for the file, “composite_edit_command.cc” assigning to concern owner from GIT blame.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/099eef98bfd425d0ca08d5927831a242120c0b51

@zhuoyu.qian@  -- Could you please look into this issue, kindly reassign if it has nothing to do with your changes.
Thank You.

Not replated with my change. Assign back.

Using the code search for the file, “editor.cc” assigning to concerned owner from GIT blame.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/347966781c467bc4c35017a87ab76f63e7a7b615

dgozman@  -- Could you please look into this issue, kindly reassign if it has nothing to do with your changes.

CC'ing reviewer of the CL - haraken@, as dgozman@ is OOO.

Thank You.

Lower to Pri-3 since this is caused by unusual HTML.

@yosin, mind triaging this one?

Since real world usage of InsertList command is very low and this is only caused by very unusual HTML. we'll visit later once we fix others.

ClusterFuzz has detected this issue as fixed in range 582537:582538.

Detailed report: https://clusterfuzz.com/testcase?key=5298307304521728

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

Crash Type: Null-dereference READ
Crash Address: 0x000000000000
Crash State:
  blink::Editor::RespondToChangedContents
  blink::CompositeEditCommand::AppliedEditing
  blink::CompositeEditCommand::Apply
  
Sanitizer: address (ASAN)

Fixed: https://clusterfuzz.com/revisions?job=windows_asan_chrome_no_sandbox&range=582537:582538

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5298307304521728

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 5298307304521728 is verified as fixed, so closing issue as verified.

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