Open report in new tab is Forbidden/403 in Chrome

When I click on the expand icon in a report viewer, I end up with a 403:

That wasn't always the case. Any idea what changed, or how I can fix it? This is in Chrome, and I just discovered that it works fine in Edge. Something about my Chrome is breaking it...

Looks like Chrome has its own PDF viewer, which kicks in fine if I disable the Adobe PDF Viewer extension...