Anyone who uses Putty a lot will inevitably accidentally paste something into their putty window due to Putty’s right-click to paste default behaviour, often resulting in pasting relatively embarassing content like SQL that should never be seen in daylight, or at least a customer’s root password.
However, I found this putty enhancement request today. Note at the bottom:
And sure enough, putty supports this. It also supports “xterm mode”, which is a more standard middle-click to paste mode. Solved!