It's a cyber-security scare called that allows hackers to access your passwords and personal information.
Major Internet services have been working to protect themselves against the problem they're calling heartbleed. They are recommending that users change their website passwords -- that includes Healthcare.gov.
Officials said there is no indication that the website has been compromised, but they're making the suggestion out of an abundance of caution.
Channel 4 spoke with an Internet security expert to see how users can protect themselves.
Chris Hamer said multiple websites could be vulnerable, but it doesn't necessarily mean your information has been compromised, it's just possible. That's why healthcare.gov has automatically reset passwords and users will now have to make a new one.
"It's kind of like someone asking to borrow your phone to look up a number and in that split second they don't look up one number, they look up all the numbers that called you," Hamer said.
The key to the vulnerability is people use the same password for their email, for their banking, for all sorts of things.
Hamer said people should change their password and never use the same password on every site. That's what computer villains do -- they get your password on one site then see if they can use it on others.
"Always have different passwords on different websites," Hamer said. "That way if one gets compromised, they don't have your email (and) your banking."
Officials said the government's heartbleed review is ongoing and users of other websites may also be told to change their passwords in the coming days.
The heartbleed computer bug has caused major security concerns across the Internet and affected a widely used encryption technology designed to protect online accounts.
Officials insist on anonymity because they are not authorized to discuss the security review by name.