A customer's complaint about my product just went viral on social media, what do I do in the first few hours?

The first six hours decide the narrative, after that, virality takes the wheel and you're reacting to a story instead of shaping it, so post a quick, honest acknowledgment ('we've seen this, we're looking into it, here's when you'll hear more') even before you have full facts, rather than going silent while legal drafts a statement. Get the facts internally in parallel, what actually happened, how many customers are affected, is there a real safety issue, because your second post needs to be substantive, not just another 'we hear you'. Silence and generic corporate language are what turn a single bad complaint into a pile-on; a fast, human, specific response is what stops it.

A quick summary to orient you. The real value is below: the resources worth your time, from people who've actually done it, not us.