I'm using gPodder 3.10.17 (2020-11-23) on Windows 10, 64-bit. The installed version.

This specifically refers to the extension under Interface called "Open website" episode and podcast context menu. This file looks relevant: https://github.com/gpodder/gpodder/blob/master/share/gpodder/extensions/episode_website_context_menu.py

Each podcast episode has a right-click menu, which has an "Open website" item when that extension is active. This item is always enabled, even if there's no website associated with the episode.

If there is an associated website, it performs as expected: it opens the website. Example podcasts with episode links:

• https://feeds.megaphone.fm/darknetdiaries
• https://feeds.simplecast.com/JT6pbPkg

If there is not an associated website, Windows Explorer opens and shows C:\Program Files (x86)\gPodder. For me that's the folder with "contents.txt", "uninstall.exe" and a few folders. Example podcasts with no episode links:

• http://feeds.gimletmedia.com/heavyweightpodcast
• https://feeds.megaphone.fm/TPG9562451353

My suggestion would be to disable the "Open website" menu item, if there's no website associated with the episode.