Taxi group Blue Bubble says its app is secure and no customer information, including credit card details, is compromised by using it.
Vulnerabilities which could be exploited to get registration information such as email addresses and pin numbers used to access the app were discovered by security experts but the company said this had already been fixed.
"We can guarantee that none of these vulnerabilities compromise any credit card or payment information which remains secure at all times," said Blue Bubble boss Bob Wilkinson.
As soon as the vulnerabilities were brought to their attention, Blue Bubble had them fixed, he said.
Mr Wilkinson recommended customers upload an update to the app and to change their app pin access number via the Blue Bubble website.
"The privacy and security of our customers' Blue Bubble registration information is always of the paramount importance," said Mr Wilkinson.
"We continue to work to ensure that all data is protected by using security systems that exceed industry standards."