Which? has accused Booking.com of "systemic security failures" after researchers successfully created a fraudulent advertisement for 10 Downing Street on the platform on 18 June. The listing, headlined "1 bedroom apartment in the heart of London," featured the Prime Minister's residence and promised a four-minute walk to the Houses of Parliament. Booking.com processed payment for a week-long stay from a researcher, and funds remained unreturned for over six weeks. A fake review rating the stay as "exceptional" and mentioning "hanging out with Larry The Cat" was added almost immediately despite Booking.com's claims of moderator checks.