Does this appear when you’re not logged in, viewing the website in a different browser or on a different computer? I browsed around the website and did not see any reference to this type of link or anything like this in my URL bar.
My guess would be it’s either plugin related or cache related ( as in a cache-busting method ). You could go through some debugging methods such as:
1) Try in a different browser, on a difference computer. If the issue is gone then the issue is most likely a browser plugin.
2) Disable all plugins, if the issue is gone enable the plugins once by one until you find the culprit.
3) Change to the default 2017 theme, if it solves the issue you know it’s a theme issue and you should contact the theme developers.
4) If you’ve tried the above and the issue continues to persist you could contact your hosting provider to see if they know the cause.