Show site information, then Connection for https://support.mozilla.org indicates
Verified by: Amazon
Why is this? Is Amazon spying on me?
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https://support.mozilla.org's certificate is signed by the Amazon Certificate Authority, Amazon Trust Services. This is widely considered a trustworthy third party for signing certificates, and your browser is apparently configured to trust certificates signed by Amazon Trust Services without prompting you.
There are many Certificate Authorities in the world, which sign certificates for individual web sites. There is no single universal authority that validates websites; each browser picks a set of CAs that they will trust by default, but you can configure trust, sometimes for the browser specifically and sometimes for your operating system as a whole. (It depends on the browser and OS in question.)
In theory, a rogue CA can issue fraudulent certificates and do things like spy on you. Any CA could do that, not just Amazon. In practice, CAs are trusted precisely because they are trustworthy. It is unlikely that they would abuse that trust, but it is not impossible. For example, when Symantec had issues with their security, browser vendors stopped trusting certificates signed by Symantec.