Hi HCP,
Thanks for your response. I managed to do the background checks like you've asked and all the background checks turned out fine.
The browser history turns out good:
It shows I visited
https://download.electrum.org/3.1.0/Electrum-3.1.0.tar.gz and also downloaded the .asc file similarly.
GPG verification output came out good:
gpg --verify Electrum-3.1.0.tar.gz.asc Electrum-3.1.0.tar.gz
gpg: Signature made Monday 05 March 2018 09:20:02 PM IST
gpg: using RSA key 2BD5824B7F9470E6
gpg: Good signature from "Thomas Voegtlin (https://electrum.org) <thomasv@electrum.org>" [ultimate]
gpg: aka "ThomasV <thomasv1@gmx.de>" [ultimate]
gpg: aka "Thomas Voegtlin <thomasv1@gmx.de>" [ultimate]
So, finally I went into Electrum's IRC chatroom and Thomas and others have helped me out. They've confirmed that it was a future functionality that Thomas was working on and he had forgotten to remove it. I can also confirm that on the Windows standalone installer, the plugin doesn't exists. So I guess it exists in the Linux source file that I downloaded from the downloads page. I'm glad it's no malware.
Here's the IRC discussion:
Thanks for helping out!