WordPress 4.7.x: Issues Uploading Images (or other media)

On Friday, February 10th 2017, one of our multi-site WordPress installs began giving errors when attempting to upload media (images, etc.) and would not allow uploads. “docname.png” has failed to upload. Sorry, this file type is not permitted for security reasons. After a big of Googling and reading, I found a post that helped. It … Read moreWordPress 4.7.x: Issues Uploading Images (or other media)