When using a Microsoft Office application you create saved workbooks that help you use the undo button and identify that the document belongs to you. However, this important tool in editing documents has a flaw in it. When malicious actors, or hackers, want to gather information about a target they look for Microsoft Office documents like Word, Excel, or PowerPoint. These documents can have information about your username, see changes that you made, comments left on the document and other types of information. 

It is recommended that when sharing a document outside of the City of Portland that you export the document into a PDF. Do this especially if you are sharing document on a publicly accessible website, this means anyone can search and download the document. Sharing within the City's network should keep you safe, as long as you trust the person you are sending the information. If you want to see other ways to deleting this metadata, or want more information, take a look at this support page from Microsoft: 

https://support.office.com/en-us/article/Inspect-documents-for-hidden-data-and-personal-information-85951777-89dd-45dd-960a-fc979414e8fc