weird MS Edge browser attemted hack ?

Someone used Edge to attempt to login as user 'meisterB' in one of my financial accounts, as when I opened Edge and went to that website, the username meisterB was filled in as if remembered. I never use Edge, never, except this time. It worries me. This happened while I have had Windows Defender and Malwarebytes Premium up to date and running. Wtf?

I did a clean install of Windows 10 about two months ago, and I use Firefox 99.9999999% of the time. I just do not get how the above happened, what might be going on, seem very suspicious.

I have installed several open source software programs, could one of them be behind this, even with my anti-malware allegedly providing real time protection? Should I uninstall some of the open source software to protect myself? I also installed a free version of DxO optics Pro 9, that is not opensource. I have never had issues with opensource software in the past (7-zip, Libreoffice, Abiword, Clementine, Greenshot screenshot grabber, etc)

Any thoughts, suggested actions? Or do I just let go of this?

Here is a list of my current opensource software, which I have never had issues with for years:

• VideoLan VLC media player
• Sumatra PDF viewer
• Tea text editor
• Musescore 2
• 7-zip
• Abiword
• ASIO4All
• Free RAR Extract Frog
• Gedit text editor
• Tea text editor
• Libreoffice
• GIMP image editor
• ImageMagick

Here is a list of new opensource software I installed recently:

• Clementine music player
• Greenshot screenshot grabber
• Irfanview image viewer
• Lightspark (replacement for flashplayer)
• pnotes sticky notes

Here is a list of closed source software I installed recently:

• Magical Jelly Bean Keyfinder (to discover Windows product key)
• DxO Optics Pro 9 free image editor