SMS alerts for Westfield Miranda and Hurstville car parks have been suspended because the feature allows people to track the movements of others.
The move affects four centres where ticketless parking has been introduced. Bondi Junction and Doncaster in Victoria are the others.
Shoppers were advised the time they entered, and when their free parking was due to end.
However, it became apparent that people could provide a false number plate when they registered their vehicles, enabling them to track the movements of others.
A spokeswoman for Scentre Group, operator of Westfield centres, said, "In an effort to upgrade security around the SMS feature of the ticketless parking system in place at four Westfield centres, Scentre Group elected to temporarily suspend the SMS reminder service”.
“While the rest of the system will continue to operate we made a decision that a risk, no matter how small, was more than we were comfortable with when it came to the privacy of our shoppers,” she said.
“Prior to launching ticketless parking, an assessment of privacy and risk was undertaken, but subsequent reviews led us to the decision that an upgrade was required, and we’re currently working through a number of scenarios.
“Some of them are short to medium-term and some are more long-term, depending the level of complexity – technical or otherwise.
“While we look forward to reinstating the service, we’d like to be as sure as possible that the risk of any privacy breach is mitigated.
‘Privacy is a priority for us – as is the confidence of our shoppers - and if we don’t believe one of our systems measures up, we’ll continue to make adjustments until it does.”