How can i parse the value in this line

I have the following line. I would like to parse the githash from it. [08/Oct/2019:05:08:31 +0000] 200 \"GET / HTTP/1.1\" 1203 \"-\" ,"source":"stdout", "tag": test/test-ui:b1cd4er8590rj39d39309e9e9/test-ui/03e020671f70 When I run my splunk query, I want to display "b1cd4er8590rj39d39309e9e9".