Please advise

Hi so i’m little worried if somebody is trying to hack my site in someway and i think that it that they are doing something with my WPJM plugin.
So i noticed with my WordPress statistics that in one day i get like 500 visits only to this link:
mywebsite.com/wp-admin/admin-ajax.php?action=job_manager_get_listings&search_keywords=&search_location=&search_categories[]=&filter_job_type[]=freelance&filter_job_type[]=full-time&filter_job_type[]=internship&filter_job_type[]=part-time&filter_job

My listings are protected tho (only subscribers can see them)
But what are they trying to achieve? Is this dangerous? Any advice on how to protect listings more deeply(so that only subscribers can see them)

Thanks

https://ww.wp.xz.cn/plugins/wp-job-manager/