If you happened to be at Park Street yesterday and noticed a cone alerting you to a broken step, you can thank Odd Onsentino, who reports what happened after he spotted the saggy stair:
Informed an employee and asked them to shut the stairwell down. He told me he wasn’t authorized to do so. I tried to reason with him, but that proved impossible. I found a cone, not too far away, and placed it in the stairwell.
An MBTA spokesman reports workers repaired the stair last night, and forwarded these photos, showing the new stair covering about to be glued down and then the completed step: