Students running the latest version of Safari (11.1) are unable to submit files to Blackboard assignments.
Having attached a file, clicking Submit results in a wait of several seconds, then the following error is displayed at the top of the page:
Failed to submit Assignment. Please try again.
Note that this does not affect submissions to Turnitin assignments.
Blackboard assignments are indicated by the an icon resembling a piece of paper next to the submission link: