In this blog will see how to detect permission changes in SharePoint. To achieve this follow the below simple steps.
First you have to go to Site Settings → Site Collection Administration → Site collection features → then choose “Reporting” → and press “Activate”.
After doing this again go to Site Settings → Site Collection Administration → Site collection audit settings → then mark “Editing Users and Permissions” events to audit in “List Libraries and Sites” settings.
Then you need to navigate to Site Settings → Site Collection Administration → Site collection audit settings → here set “Automatically trim the audit log for this site?” to “Yes” → then set trimming range time (30 days default) → here you have set the location you want to save the log before it will be trimmed → Click “OK”.
Finally go to Site Settings → Site Collection Administration → Audit log reports → Choose “Security Settings” now you have report to view all permission changes made in your SharePoint.
Also you can save this report for further analysis.