I was able to contact the author, who uploaded version 1.3: http:// www.guillermomolina.com.ar/en/files/category/3-firefox-kde5-wallet. This version fixes the bug.
On Saturday, June 17, 2017 5:13:19 PM EDT Legimet wrote: > My system just updated to Firefox 52.2.0, and passwords are no longer > autofilled. I found that after installing version 1.3 (from AMO), it works > as expected. The only issue is finding the source code. There is an SVN > repo, but it doesn't have the latest version. I tried contacting the > author, but the CAPTCHA on the contact page is broken.
