B&Q says it has taken action after being told that it exposed details of suspected store thieves to the net without password protection.
The matter was brought to light by a security researcher last week.
He said the DIY chain had taken the data offline, but was unable to get a response from the company himself.
“We have closed the issue down and are continuing to investigate how it occurred,” a B&Q spokeswoman told the BBC on Monday.
According to Lee Johnstone, chief executive of Ctrlbox Information Security, the exposed records included 70,000 offender and incident logs.
Read more on BBC. This is yet another example of a company not responding directly to a notification. It’s not enough to just take the data offline or secure it. If you receive a notification, THANK the researcher who took time out of their life to alert you that you have a problem that needs addressing. The researcher who notifies you is not your enemy and you are only inviting horrible press by engaging in ostrich-like behavior.