All the search results returned by Google on Saturday between 6:30 a.m. PST and 7:25 a.m. PST came packed with the same warning: "This site may harm your computer", inviting users to choose something else. Needless to say, there was no alternative.
Google flags search results with the afore-mentioned message only if the link in question was previously tagged as malware by non-profit StopBadware.org.
Marissa Mayer, VP, Search Products & User Experience, explains on the official Google blog:
“We periodically update that list and released one such update to the site this morning. Unfortunately (and here’s the human error), the URL of ‘/’ was mistakenly checked in as a value to the file and ‘/’ expands to all URLs. Fortunately, our on-call site reliability team found the problem quickly and reverted the file.”
Mayer also promised that new “more robust file checks” are to be put in place so further mishaps would be prevented.