The website Booking.com has launched an investigation after a hotel used a guest's personal details from a confirmation email to post a fake review.
MoneySavingExpert.com (MSE) warned that information contained in Booking.com confirmation emails could be used to hack into, change or cancel a booking, or leave a fake review.
The issue came to light after Booking.com customer Tania Wittensleger discovered a review written in her name of the hotel she chose for a three-night stay in Fes, Morocco. She said she selected it in part because of other favourable reviews, which read: "All in all a very good hotel. Lovely staff ... that is keen on fulfilling even special requests."
Booking.com only lets verified guests log in and leave reviews, but Wittensleger remembered that a manager at the hotel had photographed her Booking.com confirmation email.
She later realised that her PIN number and booking reference in the email were used to log into her booking on the site and post a review.
A Booking.com spokeswoman said: "The manager at the accommodation did indeed break the rules by photographing Wittensleger's booking confirmation and subsequently using the information collected, including the reservation ID and PIN code, to fraudulently leave a review on her behalf."
She added: "The opinion of online reviewers ranks third after price and location as the biggest influencer in a booker's decision - that's why Booking.com always ensures its reviews are verified.
"In the event that we detect or are made aware of a fraudulent review, our dedicated guest reviews fraud team will investigate fully and remove all reviews that are found to be fake. If we suspect one of our accommodation partners of submitting fraudulent reviews, we take the investigation and potential resulting consequences very seriously, and will terminate our working relationship with the property if the behaviour does not cease.
"On this occasion we are conducting a full investigation with the hotel, having already removed Tania Wittensleger's review in addition to a number of other reviews, to prevent this unfortunate experience from happening to anyone else."