Eurovision fans who have booked rooms for May's song contest in Liverpool are having their data put at risk by scammers targeting hotel chains.
Booking.com confirmed to BBC News that "some accommodation partners had been targeted by phishing emails" but denied it had suffered a data security breach.
Customers are advised to speak directly to their hotels if they have concerns.
The travel company said "a number of accounts" had been affected by cyber-attacks which were "quickly locked".
It claimed some businesses had "accidentally compromised their own internal systems by clicking on links contained in these messages".
BBC News has been unable to verify how scammers got customers data. However, a number of fans of the song contest contacted the BBC's Eurovisioncast podcast, outlining their experiences of almost falling for scams relating to accommodation booked for Eurovision in May.
Booking.com said it had "actively been supporting our partners, as well as any potentially impacted customers" and continued "to make security and data protection a top priority".
Marc Deruelle booked an apartment through the travel site, for himself and three friends to stay in Liverpool "for a pretty decent price" during the competition.
In early February he was contacted on WhatsApp by someone claiming to be a receptionist asking initially if he needed parking, and then claiming there was an issue with his payment, with a similar issue appearing on his Booking.com account.
"I thought this must be OK," he tells BBC News. "I got a text message from my bank and I had a phone call from them and they said someone was trying to scam me out of my money."
About £800 was being transferred to Uganda, but the transaction was cancelled.
"I felt really stupid because I've never been close to being scammed," he says. "It just took the enjoyment out of it and I don't want to go any more because they'll know all my details and know I'm away from home, so I cancelled it."
Marc phoned his accommodation supplier, which told him it had heard similar stories, which the BBC has been able to confirm.
This video can not be played
The rundown on the 2023 contest in 50 seconds
UKHospitality, which represents more than 700 companies, says it is always best to deal directly with hotels, rather than third-party booking platforms, if customers have concerns.
"Hotels will very rarely contact you on WhatsApp," chief executive Kate Nicholls says. "For the first time you've got lots of young people in particular who won't be usually booking and travelling to these events and [scammers] are exploiting those people who are vulnerable."
Phishing scams like this are believed to stretch wider than Eurovision and the city of Liverpool.
Booking.com confirmed that no legitimate transaction would ever require a customer to provide credit card details by phone, text message or email.
All the build-up, insights and analysis is explored each week on a new BBC podcast called Eurovisioncast.
Eurovisioncast is available on BBC Sounds, or search wherever you get your podcasts from.
Eurovision 2023 tickets sell out after huge demand
Eurovision to get £10m from UK government
Ted Lasso's Hannah Waddingham to co-host Eurovision
Biden v Trump: The sequel few Americans want to see
Pioneering singer and campaigner Belafonte dies aged 96
US woman arrested in Sydney airport with golden gun
Facebook work filtering posts 'cost me my humanity'
Mass graves of starvation cult exposed in Kenya
The woman running Biden's 2024 campaign
Which other A-lister watched Wrexham game? Take our quiz
On a bus out of Sudan with Mario the pug
The Ironman unbroken by a bomb
Why some people wake up unable to move
UK citizens tell of attempts to escape Sudan
Len Goodman: From London's East End to Strictly stardom
Where people drink beer for breakfast
Eight of the best films of 2023 so far
An ancient trick to think more wisely
© 2023 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.