How digging into an on-call issue led to an unlikely culprit

What in tarnation?
During one of my on-call rotations for our internal tools team, we got a report that Chrome was crashing for users of Gusto’s internal software. This was causing all sorts of interruptions to our normal customer service. Gusto employees in the middle of answering customer emails or phone calls might suddenly find themselves without visibility into customers’ accounts necessary to do their jobs.

This was fairly far outside the usual scope of our on-call issues. Our team is generally well-insulated by other teams from issues like browser compatibility, so I didn’t know the first thing about browser…