While much of the internet's functionality can be represented in the browser through images, text, and video, file and link sharing are an essential component of online platforms that enable collaboration, aggregation and organization.
Of primary concern with link and file sharing is the way that extracting content out of a browser exposes the user to additional risks that the perimeter of a browser and the platform usually constrains, first and foremost being Malware and its sub-variants. But file sharing also brings along with it other risks, like the storage and distribution of illegal material like CSAM, and the abuse of storage capacity.
Files and links might seem at first to be distinct categories of ideas, but since links can be used to initiate a file download from a browser automatically, integrity issues around links can be viewed as a superset of integrity issues around files. Links also have two wrinkles to them that complicate their effective moderation. Firstly, the owner of the linked-to-page can change where a link goes or what it shows dynamically, without changing the link's value (i.e. a link to "bestofbuys.co" could redirect to Best Buy today, and a malware site tomorrow). Secondly, the linked content may go to a page which violates the community standards of the platform, but this leaves platforms in a tricky spot - should a platform try to enforce their standards outside of their territory by not showing links to sites that show content that is against their Terms of Service, or should they allow this one-click sidestep of their rules?
Unfortunately, there aren't easy answers when it comes to links and files, but a few small interventions can help limit the surface area that platforms leave open for harm.