This is a serious security regression. If you are not able to fix this quickly, please revert the change that introduced it.

If this doesn't affect a release branch, or has not been properly classified for severity, please update the Security_Impact or Security_Severity labels, and remove the ReleaseBlock label. To disable this altogether, apply ReleaseBlock-NA.

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Looks very similar to  issue 736986 .

Assigning this to mlippautz@ for now. Michael, please feel free to un-assign if this is not related to your changes.

Similar, Keishi, does this by chance ring a bell? We haven't changed the base infra for some time now, so this is a bit of a surprise.

Same here. Module loading related.

I might have some time on the train where I can try to spot the issue. Wanted to assign the proper bug owner though.

In CQ https://chromium-review.googlesource.com/c/554438/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/754391155e5467e1bbe6679c32745bc2d1a8797b

commit 754391155e5467e1bbe6679c32745bc2d1a8797b
Author: Kouhei Ueno <kouhei@chromium.org>
Date: Thu Jun 29 12:03:50 2017

[ES6 modules] Add missing Trace(LocalDOMWindow -> modulator_)

Bug:  736943 
Change-Id: I13932a19dc22ba1431ca47bbfb7038f79e6e9928
Reviewed-on: https://chromium-review.googlesource.com/554438
Reviewed-by: Taiju Tsuiki <tzik@chromium.org>
Commit-Queue: Kouhei Ueno <kouhei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483330}
[modify] https://crrev.com/754391155e5467e1bbe6679c32745bc2d1a8797b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp

ClusterFuzz has detected this issue as fixed in range 483281:483374.

Detailed report: https://clusterfuzz.com/testcase?key=5223648893075456

Fuzzer: inferno_layout_test_fuzzer
Job Type: linux_ubsan_vptr_content_shell_drt
Platform Id: linux

Crash Type: Bad-cast
Crash Address: 0x1257d4825010
Crash State:
  Bad-cast to blink::TraceWrapperBase from invalid vptr
  blink::ScriptWrappableVisitor::DispatchTraceWrappers
  blink::TraceTrait<blink::Modulator>::TraceMarkedWrapper
  
Sanitizer: undefined (UBSAN)

Recommended Security Severity: High

Regressed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_content_shell_drt&range=482161:482274
Fixed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_content_shell_drt&range=483281:483374

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5223648893075456


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.

This bug has been closed for more than 14 weeks. Removing security view restrictions.

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