It is unfortunate that you have fixed your attention on an application that has nothing to do with the alert information you have.
The consequence of this is that the root cause of the alert(s) is not addressed and the issue is not actually addressed.
"The page..." That's a web page you visited. -No version of Adobe Reader opens/displays/renders web pages.
Reader (all versions) can only open PDF files.
You got to the web page by using a web browser. - No version of Adobe Reader is a web browser.
The web page (not Adobe Reader) asks to browser (which is not any version of Reader) to load a browser plug-in (which are for browsers and not any version of Adobe Reader).
The browser (not any version of Reader) does not fulfill the request and annoyed by the request the browser (not Adobe Reader - any version) provides the computer user an alert.
n.b.: "browser" MS Internet Explorer, Google Chrome, Firefox, etc.
Be well...