This QR generator works using Javascript, entirely within the page, no data is passed back to my server. Notwithstanding this, it is a good idea to save your own copy of this page, you can run it completely off-line and compare the source with the Github original.
Source code by Kazuhiko Arase: GitHub, MIT License.
This will work even if your Wi-Fi network name (SSID) includes spaces, but do note that both name and password are case sensitive.