SINGAPORE - Several Singtel customers were unable to log in to the telco's mobile application on Tuesday morning (March 1), hours after a software glitch on Monday night allowed customers to see the personal information of another customer through the app.

It raised concerns of privacy and account security among telco customers, who said on Singtel's Facebook page on Monday night that, instead of their own account, they were logged into a different account and could view personal details, such as the name and address, of a different customer when they opened their My Singtel app.

The app can be used to check and pay bills, view data usage and recontract or buy a new phone.

"I think there is a serious breach of account confidentiality and I suspect my account is also being compromised," said Facebook user Wilson Siak.

Some users also reported seeing unusual messages on the app's account information and billing pages, including one insulting Prime Minister Lee Hsien Loong.

This was because the data field under account information can be edited according to user preference, and is commonly used by customers to add information about what the account is used for.

The Straits Times understands that customers who had been redirected to this customer's account were able to modify this data field and write nonsense phrases and messages.

Subsequently, customers who logged in later and who were also redirected to this account saw what the previous customers had written instead of the original data there.

"The said pages carrying 'unusual messages' could have been mischievously modified multiple times over and screenshots taken and circulated. These messages did not come from Singtel," said the spokesman.

The issue continued into Tuesday morning. Customers also reported that they were were unable to log in to the app even after resetting their passwords.

Singtel said in a statement that it had suspended the app after information of one of their customers was "erroneously published due to a software glitch".

"We are still trying to get in touch with the affected customer to apologise and explain," said a Singtel spokesman.

"We would like to assure customers that this is an isolated incident and their account security has not been compromised."

In a statement at 11.45am on Tuesday, Singtel said customers could access the app, with most functions restored.

However, the company is still working to reactivate the app's bills, rewards and e-appointment features.