Is this normal? Why is the Add-on named "x"? - not just this one, any add-on that I want to install named "x"..
p.s.: from the https://addons.mozilla.org/en-US/firefox/ site
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It seems like that URL points to Adblock Plus (as does the author's name). My guess is that something was accidentally pushed to release with a placeholder for the version / name. I tend to use "x", and various combinations of "foo" and "bar".
Unfortunately, your question doesn't give me anything else to go on and is too point-in-time to really get anything useful.