Microsoft To-Do allows users to attach files to tasks that are not larger than 25MB. Images, documents, and other files can now be attached to tasks so that they can be accessed across all devices that are logged into the same account. This is very useful when creating shopping lists and you want to attach images of products that you are looking to purchase. This feature is available in the beta builds of Microsoft’s version 1.49.1901 and greater on Windows 10, iOS, and Android.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-to-do-beta-finally-lets-you-attach-files-to-tasks/