This is most likely related to:
<a href="https://github.com/netdna/bootstrap-cdn/issues/128" rel="nofollow">https://github.com/netdna/bootstrap-cdn/issues/128</a><p>All .js files on BootstrapCDN were distributing exploit code until it came back online (within the last 3 hours)<p>Oddly, there is no mention of this anywhere else.
The relevant link is here:
<a href="https://netdna.bootstrapcdn.com" rel="nofollow">https://netdna.bootstrapcdn.com</a><p>Not sure how long it has been down for but I became aware of this about a half an hour ago.