A cyber attack on karaoke bar chain K Box has left its members crooning the blues and crying for swift action, after their personal data, including their home addresses, surfaced online.
More than 300,000 people on K Box's membership scheme are affected by the leak.
One of them, university student Ms Lee, 20, said she is thinking of making a police report.
"All my private information is in the list. I keep thinking about the things people could do with the information obtained," she told The Straits Times.
"This shows a serious lapse in K Box's security system."
Another K Box member, 28-year-old Ms Kwek, said she counted four other friends who were on the list as well.
"I got the membership card during my secondary school days but it must have been more than five years since I last used it," she said.
Ms Kwek, who works in the finance industry, said she had considered making a police report but felt it was of little use.
"You can make a report but so what? The information is already out there right now."
The victims declined to be named in full, fearing further privacy breaches.
The list also contains the particulars of at least two local television celebrities, a check by The Straits Times showed.
A hacking group which calls itself The Knowns had leaked to various media outlets a list containing the names, addresses, e-mails, and phone and identity-card numbers of those holding a K Box membership card.
In an e-mail titled A Warning To Singapore Government, the group said it was releasing the information as it was unhappy that toll charges will soon be increased on this side of the Causeway.
"The selfish act increases the revenue of the Singapore Government at the expense of the common people," it said.
The Straits Times, Mediacorp, and socio-political site The Real Singapore were among those that received the e-mail. The Real Singapore reproduced a screengrab of the e-mail, which showed a link to the leaked information, on its website and its Facebook page.
Financial adviser Mr Tan, 26, said he was angry but "there is nothing I can do now".
"How can K Box compromise on its IT security? Customers' information is the most important," he said. "Even my home address has been leaked. I feel very insecure now."
None of them has been contacted by K Box.
Ms Lee added: "I think K Box should at least explain the incident to its customers."