We have updated the default competition docker image to codalab/codalab-legacy:py39. It is the image in which the submissions of a competition are run if nothing particular is set up by the organizers.
If your competition was using the default image, and you want to keep the old behavior, you can come back to it by setting the docker competition image to codalab/codalab-legacy:py2 in the editor, as shown in the screenshot below.
You can also add the following line in the competition.yaml file:
Thank you for your comprehension.