Adobe Flash Player Update

Ignore the suggestion provided by miyalung. You do not need to install Java.

Read this user tip by John Galt: Beware bogus Adobe Flash "installers" - Apple Community:

• "The only correct response to those bogus messages is to ignore them. Close the web page.
• If you can't close the page, please read Phony "tech support" / "ransomware" popups and web pages for the solution.
• Consider clearing Safari's history so that you don't inadvertently navigate back to the same bogus webpage.
• Never react to such a popup by downloading and installing some magical fix for a problem that doesn't exist.
• There are no consequences to the mere appearance of these phony "updaters".
• As long as you did not succumb to the attempted scam by downloading whatever junk it's attempting to convince you to download, no other action is necessary, or justified."

Be sure to read the entire User Tip, that was just an excerpt.

Can you try installing this : https://support.apple.com/kb/DL1572?locale=en_US

Then restart the Mac and see if the flash player update will still appear.

You are welcome.