Unable to submit to Blackboard assignments using Safari

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: