Steps to Reproduce:
Edit page source both using the new and the old editor and enter something like e.g. /usr/share/wine/wine.inf or wine/wine.
Now watch the preview and you will see something like /usr/share/wine.inf or wine. If you publish your changes the correct string will be saved and shown.
Actual Results:
wine/wine becomes wine and /usr/bin/wine/wine.inf becomes /usr/share/wine.inf in page preview when editing source
Expected Results:
wine/wine and /usr/bin/wine/wine.inf are shown as this in page preview when editing source