Universal Containers (UC) is planning to deploy a custom mobile app that will allow users...

The most recommended and secure OAuth scope setting for UC’s custom mobile app is custom_permissions. Custom_permissions are settings that can be used in Apex code or validationrules to check whether a user has access to a custom feature or functionality. Custom_permissions can also be used as OAuth scopes to limit the access of an external application, such as UC’s mobile app, to certain custom features or functionalities in Salesforce. By configuring custom_permissions as OAuth scopes in the connectedapp settings, UC can restrict the mobile app access to only the e-signature feature and protect against unauthorized or excessive access.

The other options are not recommended or secure OAuth scope settings for UC’s custom mobile app. Id is an OAuth scopethat allows the mobile app to access basic information about the user and their org, such as name, email, profile picture, and instance URL. This scope does not provide any access to Salesforce data or features, such as uploading e-signatures. Web is an OAuth scope that allows the mobile app to access Salesforce data and features through a browser or web-view. This scope provides full access to Salesforce data and features, which could expose sensitive information or allow unwanted actions. Api is an OAuthscope that allows the mobile app to make REST or SOAP API calls to Salesforce using the access token. This scope also provides full access to Salesforce data and features, which could compromise security and compliance. References: [OAuth Scopes], [Connected Apps], [Custom Permissions]