I decrypt the passwords and put everything in a text file on the local machine.
How do you save the file on the local machine? The only way that is possible is through the user 'downloading' the file to save it locally, or using a browser plug-in, which they must install.

When the user downloads it, they can also click 'open' instead of 'save', and see the text file immediately. If they save it, then they must navigate to it and open it themselves.

The browser will not allow you to execute files or shells without an integrated assembly (plug-in), which the user would have to install first by downloading it from your website. Otherwise, websites could launch your disk degragger or format your c-drive when you visited them.