Steps to Reproduce: Here's a link to what happened:
The editor used the Visual Editor to change a typo in an image caption. Presumably, a developer could go to that previous version of the article and try to edit the image caption using VE to reproduce this bug.
Actual Results: The Visual Editor added a link= parameter with a modified version of the image file name, and it added an empty alt= parameter.
As a side effect, because the file name was HTML-ized and there appears to be a bug in image syntax processing, the link= parameter and value were displayed as the caption. See T216003 for that bug report.
Expected Results: VE should not add a link= or alt= parameter unless the human editor requests them.