No idea what Outright is and don't use seller hub, but suspect you're using newer Chrome (or maybe Firefox) and the browser is complaining about an HTTP:// link to Outright (browser wants to see all HTTPS:// links when coming from HTTPS://pages) Part of the new era of annoying "protect me from myself" and "there is a man in the middle attack hiding under every bed" thinking.
Could be that the eBay link is HTTP://, but gets redirected by the Outright server to an HTTPS:// at that point, but the browser throws its complaint at the original launch point on the Seller Hub page.
Fix? Assuming my speculation is correct, it's just another HTTP:// link the eBay coders need to update to an HTTPS:// link. In the meantime, ignore the error (unless you are worried about Martian elite hackerzez intercepting your communications), or use something like Redirector or HTTPSAnywhere addons (or whatever is avail for your browser) to fix up those links to be HTTPS:// at launch (when you click them).
With the addons the browser might still throw a fit - don't know if the addons do the fixups before or after the browser complains - but since the targets would be changed to secure HTTPS:// links you could ignore the warning then without compromising sekooritee.
