You receive some type of communication (in my case a message on 'WhatsApp") from a hotel you have reserved informing you that your reservation was flagged as "suspicious" and that you need to make a further payment through some link to "keep your booking active" or it would be cancelled.
To my eyes this had scam written all over it, and apparently even though I've discovered it's commonly known I'd never heard of it before.
They had my dates of stay correct and I booked directly with the hotel so looks like the hotel system was hacked.