I once was changing the pricing for the primary subscription product for all 8000+ users registered in our CMS, and accidentally resumed the subscription and ch

I once was changing the pricing for the primary subscription product for all 8000+ users registered in our CMS, and accidentally resumed the subscription and charged 300+ customers $75 who had cancelled the plan months or even years ago. The payment platform's API's `updatePlan` function had an optional flag for `reactivateSubscriptionAndBillImmediately` with default value of `true`, as it turns out. I had to stay up till 6AM writing a script to detect all of them, refund their money, send an apology email with some free credit, and cancel their subscriptions, and also write a note to my cofounders outlining the situation so they could crisis manage while I was out cold. After which I wrote an angry email to the billing platform (probably harsher than they deserved given I didn't test their API appropriately on our dev instance). To their credit, they promptly changed the default. They were a young company and apparently not that many clients had used that API endpoint before. It resulted in some very angry customers threatening to cite us to various business practice enforcement bodies around the world, but all in all some floor-sweeping profuse apologies and prompt action laid concerns to rest and no harm was done.