special character at end

Not in WordPress itself, no. Have you tried:

– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).

– switching to the default theme to rule out any theme-specific problems.

– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.

– re-uploading all files & folders – except the wp-content folder and wp-config.php & root .htaccess files – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.

Esmi
You were correct – I deactivated the plugin ShareThis and it fixed the problem
Clearly that plugin has bugs

Might be worth reporting the issue to the plugin’s developer. Glad to hear that you’ve got it sorted now, anyway. ??

Normally, if someone copies the URL-string of a page or a post and sends it to someone else, you won′t be able to tell from where the second visitor got this direct link.

ShareThis has a feature to track this kind of URL-sharing. If this feature is activated, then every page that is shown on the public part of your site, will have an appended hash symbol and some random characters.

If someone later enters the same URL including this random string, then this will be tracked as a URL-sharing event.

There are several other plugins that do the same trick. But since ShareThis happened to be mentioned here (and I use it on a couple of sites) I referred to that plugin, specifically.