This indicates an attack attempt to exploit a Server-Side Request Forgery Vulnerability in Apache Solr Server.
The vulnerability is due to improper sanitation of a crafted HTTP user input. The vulnerability may allow a remote attacker to request data from internal resources that are not publicly available by manipulating the processed input stream.
Apache Solr versions before 8.8.2
Security Bypass: Remote attackers can bypass security checks of vulnerable systems to make HTTP requests.
Apply the most recent upgrade or patch from the vendor.