Last step of new instructable replaced by coding gibberish on publishing Answered

I just posted a new instructable, and the moment I hit Publish, the text of the last step became:

{"context":{"location":{"href":"https://www.instructables.com/editInstructable/publish/EP9GD9VI8J9YE52","origin":"https://www.instructables.com","protocol":"http:","username":"","password":"","host":"www.instructables.com","hostname":"www.instructables.com","port":"","pathname":"/editInstructable/publish/EP9GD9VI8J9YE52","search":"","hash":""},"spinner":{"jQuery110208686437982777664":1236},"you-image":{},"jQuery110208686437982777664":1,"gtmHasClickListenerTag":true,"b":{"sizzle-1430739270545":{"parentNode":["25480 299",48]}},"h":{}},"selector":"#editor-Object-65"}

OS: Windows 8,
Browser: Up to date FireFox