In SharePoint Server 2013, SharePoint Server 2010, or SharePoint Online, you use the SharePoint 2010 Workflow platform to configure an Approval workflow. However, when an approver tries to approve the item, he or she receives the following error message:
To resolve this issue, grant Edit access to the specific task list for the workflow to the affected user.
Additionally, the user who is approving the item as part of the workflow is also required to have Read access to the item that’s the target of the workflow.
This behavior is by design. Users who try to approve a SharePoint 2010 Approval Workflow task, but who have only Edit permissions to the task list item, can't view the task's form page. The user must have at least Read access to the workflow task list.
For more information about approval workflows, go to Understand approval workflows in SharePoint 2010.
For more information about permission levels in SharePoint Online, go to Understanding permission levels.
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