It's side effect of some annoying website ads which are targeting windows.
I found an untested but sensible solution here (in chinese)
*****/blog.0xbbc.com/2015/01/禁止广告加到safari的reading-list/
in short, install the plugin it provided
*****/blog.0xbbc.com/wp-content/uploads/2015/01/NoAdReadingList.safariextz.zip
or you can make the plugin by yourself if you worry about the security of the link above (see code at the end of this post)
Another case you cannot avoid even with this plugin, is when you search some keywords in address bar, even before you press enter, the ads url has been added to your reading list. The solution is turn of "Preload Top Hit in the background" in safari preferences -> "Search" tab.
<!DOCTYPE html>
<script>
safari.application.addEventListener("activate", activateHandler, true);
function activateHandler(event){
var _createEvent =document.createEvent;
document.createEvent= function(s) {
if(s =="MouseEvents"){
console.log("This website tries to simulate mouse events!");
returnnull;
}
elsereturn _createEvent(s);
}
}
</script>
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