happy.luckyparkclub.com

Force Quit Safari ( command + option + esc keys).Then restart Safari holding the Shift key. 

If you still have problems Empty Caches (Safari menu > Preferences > Privacy > Remove all website data. (This will also remove history if you do not want to remove History open Safari Preferences > Advanced and check mark “Show Develop Menu” then choose “Empty Caches” from Develop Menu ).

Then go to Safari menu > Preferences > Extensions and check there. If there is an extension delete it.

If the problem persists then download and run Malwarebytes. Malwarebytes was developed by one of our own colleagues here in ASC and is about the most proven anti-malware software for Mac.

Of course, if you then revisit the site that is generating the pop-ups they will return.

If someone is experiencing the issue in Chrome, this fix applies to Chrome as well.

Same happened to me on Chrome. Malwarebytes could not find anything. After scanning chrome in application support, found a reference of "happy.luckyparkclub.com" in preferences. Cleaned browsing data for longer period than it was happening. Fixed the issue for me.

Thanks everyone for helping and sharing.

You can run malwarebytes. But the only way to avoid it is to not visit the site that caused it.

You're welcome, glad it's sorted.