DOCS Add user help for securing file upload form submissions

[ci skip]

docs/en/userguide/form-submissions.md

@@ -85,3 +85,114 @@ This decides whether to send the email based on two options
 * Select the field which you want the custom rule to apply to
 * Select the condition the field must follow
 * enter for the condition (the 'is blank' and 'is not blank' conditions do not require any text)
+
+## File Upload Field
+
+[note]
+This functionality is specifically included in Silverstripe core functionality 4.6 and above, 
+[silverstripe-userforms](https://github.com/silverstripe/silverstripe-userforms/) 5.3 and above and is also included in 
+the module [silverstripe-elemental-userforms](https://github.com/dnadesign/silverstripe-elemental-userforms).
+[/note]
+
+Files and other data that is uploaded by your website visitors should be handled with care to reduce the risk of exposing sensitive data. 
+Files which are uploaded through a form inherit the permissions of the folder they are being placed into, so it's important that you 
+ensure the folder you select can only be viewed by appropriate parties. Folder permissions can be managed within the Files area.
+
+File permissions do not affect the Draft/Modified/Published state of files. Use both file permissions and Draft states 
+together to ensure your files remain safe. For example, in case they are accidentally published. 
+
+## File indicators
+
+Files have a number of icons which can help to identify the original source of a file and whether caution should be taken when using it. 
+
+**Form submission:** ![Address card icon](_images/address-card.png)
+
+This indicates a file is associated with a form submission, this file could contain personal identifiable information and care should be taken so that it is not leaked.
+
+**Form submission with warning:** ![Address card with warning icon](_images/address-card-warning.png)
+
+This indicates that a file associated with a form submission does not have the recommended permissions applied to it. 
+A caution symbol is added to the form submission icon because it has a higher risk of being publicly accessible if it is published.
+
+**Restricted access:** ![User with lock icon](_images/user-lock.png)
+
+Indicates that a file/folder has restricted access and will only be visible to certain users or groups. To learn more about the usage of this particular icon refer to 
+[File Permissions](https://userhelp.silverstripe.org/en/4/creating_pages_and_content/creating_and_editing_content/images_and_documents/file_permissions).
+
+## Overview of files with custom permissions
+
+![Overview of icons usage on thumbnails and headers in the Files area](_images/overview-icons.png)
+
+[note]
+Folder with restricted access containing files with custom permissions and their associated file icons.
+* FS - Form submission
+[/note]
+
+To get started, create a new **User Defined Form** page in the CMS. See [Creating and editing forms](creating-and-editing-forms) 
+to learn more. To add a File Upload field to the form, click on the ***Form Fields*** tab in the page editing view. 
+Click the ***Add Field*** button then select **File Upload Field** from the dropdown.
+
+![Adding a File Upload Field](_images/userforms-creation.png)
+
+### Setting up a folder to store file uploads for your form
+
+When setting up an Upload Field on a form for the first time you will receive a prompt to select an appropriate folder to store files for this form. 
+You can either create a new folder or use an existing folder to store your file submissions.
+
+The folder you select will become the default folder for this form and any additional Upload Fields which are added. 
+Each File Upload Field can use different folders for storing its files, this can be managed by editing the folder location on each individual field.
+
+#### Option 1, create a new folder (recommended):
+
+This option is only available the first time you add an upload field to your form. Once the first upload folder for the form has been established, 
+all subsequent file uploads from the same form will use this folder by default. 
+
+By default this option will store file submissions in a folder with restricted access suitable for dealing with personal/sensitive data. 
+A folder will automatically be created with the same name as the form name.
+
+It will be recommended for this folder (and the submission files) to be placed within a top level folder named ‘/Form-submissions’. 
+You can either use the suggested folder name or create your own by altering the folder name. You can also manually add deeper folder levels
+ by adding ‘/’ in the text field provided e.g ‘Competition-entries/May-2020’.
+
+By default the ‘/Form-submissions’ folder is set so only [Admins](https://userhelp.silverstripe.org/en/4/managing_your_website/managing_roles_and_permissions/#using-roles) 
+have permissions to access it (restricted access), any files or folders in this folder will inherit these permissions. 
+This can be changed manually on a per file/folder basis from the **Files** area.
+
+Click **Save and continue** to continue editing your form.
+
+![Create a new folder option](_images/modal-create-new-folder.png)
+
+#### Option 2, use an existing folder:
+
+If you choose to use a folder that already exists you can select the folder from the **Select folder** dropdown. Once you select a folder, 
+an icon will indicate whether or not the folder has restricted access and provide information for who the file uploads will be visible to. 
+
+If the form deals with personal data you will want to select a folder which has Restricted Access. 
+It will display some information about the groups who can access files in this folder.
+
+Click **Save and continue** to continue editing your form.
+
+![Use existing folder option](_images/modal-use-existing-unrestricted.png)
+
+## Changing folders for individual fields
+
+If the folder you have selected for storing files does not have the recommended view restrictions applied, files uploaded to that folder 
+which have a published state will be visible to anyone who views them, or that can guess the URL. 
+You can change the folder associated with an Upload Field at any time.
+
+![Changing a File Upload Fields folder location on an individual field](_images/userforms-documents.png)
+
+When viewing/selecting folder locations from the form you will see an icon indicating its permission status. 
+You will either see a **restricted access** icon, or a **warning** icon.
+
+To store your files in a safer manor you can do one of several things:
+* Create a new folder from the Files area, or if this is your first time setting up an Upload Field for this form you will 
+be guided through the process, for more information see [Setting up a folder to store file uploads for your form](#Setting-up-a-folder-to-store-file-uploads-for-your-form).
+* Change the upload folder to one which already has restricted access. Edit the Upload Field and select a folder from the **Select a folder** dropdown. 
+* Change the view access permissions of the current folder in the Files area to restrict access to the file.
+
+You can manage your folder permissions by navigating to the Files section in the CMS menu and edit the folders details. 
+See [File Permissions](https://userhelp.silverstripe.org/en/4/creating_pages_and_content/creating_and_editing_content/images_and_documents/file_permissions) 
+for more information and [Roles and permissions](https://userhelp.silverstripe.org/en/4/managing_your_website/managing_roles_and_permissions/) to learn more.
+
+For more information on the usage of these icons in the files area, please refer to [File Indicators](https://userhelp.silverstripe.org/en/4/creating_pages_and_content/creating_and_editing_content/images_and_documents/file_permissions/#file-indicators).