A honeypot at a client site caught this being exploited in the wild on 2022-08-09. The software, YOURLS-GA-MP-Tracking hasn’t been updated since 2016 and requests for a security contact are not answered. When it receives the HTTP referer it can use that to invoke a server-side request forgery flaw.
REDACTED - - [09/Aug/2022:19:01:32 -0400] "GET /GA-Measurement-Protocol/plugin.php HTTP/1.1" 404 737 "ATTACKER-SITE" "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36"