The Run box is safe, although not useful for multi-line content. That tweet (now deleted) was referring to the Start menu search box.
“You are correct. This traffic was not generated by typing text into the "run box", it was generated by typing text into the "start menu box". We are very sorry for the confusion this has caused.”
“You are correct. This traffic was not generated by typing text into the "run box", it was generated by typing text into the "start menu box". We are very sorry for the confusion this has caused.”