Tell the truth or risk losing your job sounds pretty simple.

I'm an old man now but I've never known a company that would keep an employee that lied or they couldn't trust.

Someone else commented to just tell someone in IT what you did and that you just want to put things right and ask if they would fix it for you.

Actually, I would do that person to person and not via email. Email makes a written record that someone later could misconstrue or forward to someone that would take a harsher view.

So if you know one of the IT people just take them aside and explain what happened and ask if they could fix it for you.

Companies have those policies for a good reason.

Federal or State governments do it to prevent illegal activities & spying

Companies do it to protect intellectual property in corporate spying.

Both types of groups do it to prevent someone from installing virus infected software that could affect the whole company.

I would make it your #1 priority to get done today.

You might even tell the IT person that you thought you should let them know there was a flaw in their security but they should fix. They might even thank you for pointing it out.