When trying to view an attachment that is present in an "event record", I am getting an error report which says:
Insufficient Privileges. You do not have the level of access necessary to perform the operation you requested. Please contact the owner of the record or your administrator if access is necessary.
This happens when a regular Salesforce user apart from system administrator tries to view the attachment associated with the event created. And this is an Enterprise Edition of Salesforce.
Best Answer
You will most likely be dealing with either Object-Level Security or Record-Level Security.
As a first step: Check that the profile of the user has access to attachments and then check the Role relationship between the user and the owner of the attachment.
Object-Level Security (Permission Sets and Profiles)
If this was restricting the "regular Salesforce user" from accessing attachments then they wouldn't be able to access any attachment records, regardless of who created the.
Field-Level Security (Permission Sets and Profiles)
FLS is unlikely to be the issue here. If that was the case, the user could access the attachments, but would not be able to see certain fields.
Record-Level Security (Sharing)
Record level security is at the actual record level.
Have a read through Securing Data Access