For µFunds developers, privacy is an important matter to care about. Fortunately, µFunds is a really simple Google Sheets addon that performs a single, well-defined task, making it really easy to explain how your privacy is respected.
When being installed, µFunds may ask permission to access your Google profile and your e-mail address. However, this permission will not be used anytime.
On the other hand, permission to access your spreadsheets and make external requests will be asked and actually used, but only when you call the µFunds function in a cell of your spreadsheet.
For specific details of how µFunds works, including where your introduced data can be sent or saved, please refer to the How µFunds works page or, if you're a developer, directly to the Code section of the GitHub repository.
As a consequence of µFunds' simple behavior, µFunds does not save your data anywhere, apart from Google Apps Script's cache. In this last case, fetches from information sources are saved for 2 hours and the relationships between asset identifiers and countries are saved indefinitely.
Only Google and the used information sources can get anonymous information as a result of a µFunds function call, probably only for statistics purposes. For more information, please refer to their privacy policies here and here.