macupdate.com says I have a virus (in safari). Should I click ok or just format my mac and start again?

The is a phishing scam. Do not click any buttons.

Helpful Links Regarding Malware Problems

If you are having an immediate problem with ads popping up see The Safe Mac » Adware Removal Guide, remove adware that displays pop-up ads and graphics on your Mac, and AdwareMedic. If you require anti-virus protection Thomas Reed recommends using ClamXAV. (Thank you to Thomas Reed for this recommendation.) You might consider adding this Safari extensions: Adblock Plus 1.8.9.

Open Safari, select Preferences from the Safari menu. Click on Extensions icon in the toolbar. Disable all Extensions. If this stops your problem, then re-enable them one by one until the problem returns. Now remove that extension as it is causing the problem.

The following comes from user stevejobsfan0123. I have made minor changes to adapt to this presentation.

Fix Some Browser Pop-ups That Take Over Safari.

Common pop-ups include a message saying the government has seized your computer and you must pay to have it released (often called "Moneypak"), or a phony message saying that your computer has been infected, and you need to call a tech support number (sometimes claiming to be Apple) to get it resolved. First, understand that these pop-ups are not caused by a virus and your computer has not been affected. This "hijack" is limited to your web browser. Also understand that these messages are scams, so do not pay any money, call the listed number, or provide any personal information. This article will outline the solution to dismiss the pop-up.

Quit Safari

Usually, these pop-ups will not go away by either clicking "OK" or "Cancel." Furthermore, several menus in the menu bar may become disabled and show in gray, including the option to quit Safari. You will likely have to force quit Safari. To do this, press Command + option + esc, select Safari, and press Force Quit.

Relaunch Safari

If you relaunch Safari, the page will reopen. To prevent this from happening, hold down the 'Shift' key while opening Safari. This will prevent windows from the last time Safari was running from reopening.

This will not work in all cases. The shift key must be held at the right time, and in some cases, even if done correctly, the window reappears. In these circumstances, after force quitting Safari, turn off Wi-Fi or disconnect Ethernet, depending on how you connect to the Internet. Then relaunch Safari normally. It will try to reload the malicious webpage, but without a connection, it won't be able to. Navigate away from that page by entering a different URL, i.e. www.apple.com, and trying to load it. Now you can reconnect to the Internet, and the page you entered will appear rather than the malicious one.

Should I click ok or just format my mac and start again?

Neither. Read "Ransomware" web pages.

Look again, that isn't MacUpdate! There isn't any such web site as "macupdate.com-apple.me".

First of all, there is no way to determine whether you have malware of any kind on your computer from the Internet. Pressing "OK" will most probably tell you to call a 1-800 number where a scam artist posing as a technician will attempt to gain access to your computer and then charge your credit card to fix a problem that either doesn't exist or was caused by them.

Yup I got the same message too but I was using chrome I enabled a security extension my internet provider provides because they give free virus protection. And scanned for viruses but no threats were found I didn't know how to force quit so I had to manually shut down my Mac. What do you recommend next time this happens? I also cleared my cache too and that seemed to help...

The next time it happens, Force Quit the browser, then start it in Safe Mode by holding down the Shift key. This prevents any windows/tabs from your previous session from opening again. Clear all your cookies/caches, and go into your History and remove the site you were on that caused the pop-up. Then download and install an ad-blocking extension. After you do this, close the browser and restart it normally.

Thanks that helped a lot🙂

Thank you so so so so much!!!!! I got really worried for a sec there even though I suspected it probably was a scam! 😁 Thank you so much Apple!😍