While working on data.census.gov, I noticed that I was able to paste data (using ctrl + v) directly into cells on an active webpage and overwrite the data that was already there. You can paste into multiple cells at once if you're copying from elsewhere in the table or an external spreadsheet. The only way to undo the paste is by refreshing the whole page.
Luckily the changes don't seem to stick when downloading the table, but this bug could be quite an issue for someone doing a quick reference-- it's very easy to accidentally paste and not notice it, since the inserted data is identical in formatting to the original data.
Hopefully this issue will be resolved by the Bureau soon, but in the meantime I wanted to alert everyone to watch out for this problematic bug!
Planning Data Intern, City of Cambridge