Salesforce Facts by Abhishek

Let's say we have made one custom field read only for a particular profile by checking the read only checkbox in field level security settings in the field security page or by using page layout. But, you found that the field is still editable by the users of the particular profile. The reason might be, we have one system permission in profile settings 'Edit Read Only Fields' which might be enabled either in the profile or in the permission set level. So if this permission is enabled, the read only fields are still editable by the profile users. So, to enforce our intended field security, we have to configure our security settings accordingly considering this particular system permission.