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

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/4c5f755739fcbe4021d3a2938571d066a1b2d5cf

@yosin -- 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 world usage of InserParagraphSeparator command is low.

ClusterFuzz has detected this issue as fixed in range 489161:489186.

Detailed report: https://clusterfuzz.com/testcase?key=5033102635433984

Fuzzer: bj_broddelwerk
Job Type: windows_asan_chrome_no_sandbox
Platform Id: windows

Crash Type: Null-dereference READ
Crash Address: 0x00000008
Crash State:
  blink::InsertParagraphSeparatorCommand::DoApply
  blink::CompositeEditCommand::ApplyCommandToComposite
  blink::TypingCommand::InsertParagraphSeparator
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=windows_asan_chrome_no_sandbox&range=456190:456233
Fixed: https://clusterfuzz.com/revisions?job=windows_asan_chrome_no_sandbox&range=489161:489186

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5033102635433984


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 5033102635433984 is verified as fixed, so closing issue as verified.

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