Predator and CL could not provide any possible suspects.
Using Code Search for the file, "CompositeEditCommand.cpp" assigning to the concern owner.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/abd14b624281e66a7990b443ddf9eb0254257081

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

Lower to Pri-3 since real wold usage of "Insert*List" command is low with unusual
HTML

Automatically applying components based on information from OWNERS files. If this seems incorrect, please apply the Test-Predator-Wrong-Components label.

ClusterFuzz has detected this issue as fixed in range 510178:510349.

Detailed report: https://clusterfuzz.com/testcase?key=5420796800663552

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

Crash Type: Null-dereference READ
Crash Address: 0x00000024
Crash State:
  blink::CompositeEditCommand::InsertNodeAfter
  blink::CompositeEditCommand::MergeIdenticalElements
  blink::InsertListCommand::ListifyParagraph
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=windows_asan_chrome&range=443510:443512
Fixed: https://clusterfuzz.com/revisions?job=windows_asan_chrome&range=510178:510349

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5420796800663552

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 5420796800663552 is verified as fixed, so closing issue as verified.

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