This indicates an attack attempt to exploit an Information Disclosure vulnerability in Joomla!.
The vulnerability is due to an error in Proclaim component when handling SQL files. A remote attacker may be able to download arbitrary backup file, via a crafted HTTP request.
Joomla! component Proclaim 9.1.1
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Currently we unaware of any vendor supplied patch for this issue.