Microsoft is still working on a security patch for Internet Explorer. A flaw was announced last week that could cause a lot of problems.
And those problems would be widespread since it's estimated that more than half of computers around the globe use the browser.
Tech expert Brad Chacos with PC World Magazine says hackers can exploit the vulnerability by getting people to go to certain websites.
"Once the bad guys gain control of your computer and have direct access to your computer, this particular exploit can let them do anything you can do," he said.
Chacos says the problem needs to be fixed -- and soon.
"Fortunately right now, it's pretty much limited to defense and finance sites, but the thing with exploits like this, is that once they're known, everyday criminals start to use this kind of stuff," he said.
Microsoft has a work-around which won't work for many since it requires changing settings on individual affected systems and disabling some functions.
People can get around the problem by using alternate web browsers such as Firefox and Chrome.