This is another extra cool forum feature.

Advanced Attachments Features

• Adds “Attach File” button in topic and post editor
• Opens an extended file attachment window
• AJAX multiple file uploading and validation system
• Visual control over multiple file uploading process
• Allows to preview, watch and listen attached images, videos and audios
• Allows to upload files by dragging them on your browser window.
• Individual media library for each forum user.
• Files can be inserted inline, between post content texts.
• Files count, size and type control system
• Powerful lightbox slider to display file attachments
• Lots of displaying options to customize all kind of media components (images, thumbnails, players…)
• Integrated with wpForo Usergroup and Forum Access permission system
• Allows to disable attachment viewing by guests and certain usergroup.
• All front-end phrases are available in setting page for quick translation to any language
• Super responsive user interface, looks nice on all devices and screen dimensions

Example: