If you query the API for tags related to [bin]: https://api.stackexchange.com/2.2/tags/bin/related?site=stackoverflow
this simply returns:
Invalid JSON returned and a 404.
But it should return:
{
"items": [],
"has_more": false,
"quota_max": 10000,
"quota_remaining": 8194
}
I guess an intrusion detection of some sort is working here?