From 11:37 AM PST to 1:24PM PST, a small number of Files.com customers experienced errors in the web interface when viewing some pages.  This was caused by a JavaScript bug introduced during a routine update, related to rendering pages with “tab-like” navigation.  Because the buggy behavior impacted only a small number of pages, it was not detected during our routine testing.

Our monitoring systems did record an increase in frontend error rates, however the increase in errors was not high enough to raise an alert and instead we were alerted to this bug through our customer support channel.

As a result of this incident, we have reduced the alerting threshold for similar front end errors. We expect that we will now detect and resolve similar incidents in the future.