Visitor is getting redirected with strange url added

I just upgraded this blog to 3.8.1. Not sure how it would have caused this.

I’ve noticed many visitors are getting redirected to the same page with some garble added to the url, which ends up as a 404. I need to stop this.

For instance: https://donnabarstow.com/park_blog/2014/01/28/missing-parakeet-in-silver-lake-reward/ then changes to https://donnabarstow.com/park_blog/2014/01/28/missing-parakeet-in-silver-lake-reward/undefined#init/fpc=7639673-143e55d76ce-30565854-1/sessionID=1391122537694.30032/publisher=2b17fc28-9f7b-45a3-8886-d5560976d80b/tracking=true/onhover=true/async=false/asyncPlusone=false/autoclose=true/autoPosition=tru for the second hit. Sometimes it goes to another page in my site that I had linked to, with same result, a 404.

I can see these results on statcounter. I looked up undefined, and some answers said Java. However, I’m not getting this problem on my other blogs.

Any suggestions? https://donnabarstow.com/park_blog/

What does undefined mean? Something about the session too long?