The download URLs may be confusing but they’re actually correct. I modified a fixlet to download all of the files using those URLs successfully:
The thing to note is that these URLs are defined inside of Relevance Substitions, so they need to be percent-encoded for Relevance strings. %25 is the percent-encoded symbol for the percent sign itself, so the relevance string {“%2520”} is equal to the literal string “%20”
Edit:
Statement in ActionScript:
add prefetch item {"name=Firefox_Setup_115.16.0esr.exe sha1=111209f78bcd004bcdd7f10732e0b03628ab6859 size=58633352 url=http://ftp.mozilla.org/pub/firefox/releases/115.16.0esr/win64/en-US/Firefox%2520Setup%2520115.16.0esr.exe sha256=4111e98f196f3f418223950649ad9e75a335a282f6169017440039e6dc58b238"}
In the Fixlet Debugger we can see how that relevance string evaluates:
q: "name=Firefox_Setup_115.16.0esr.exe sha1=111209f78bcd004bcdd7f10732e0b03628ab6859 size=58633352 url=http://ftp.mozilla.org/pub/firefox/releases/115.16.0esr/win64/en-US/Firefox%2520Setup%2520115.16.0esr.exe sha256=4111e98f196f3f418223950649ad9e75a335a282f6169017440039e6dc58b238"
A: name=Firefox_Setup_115.16.0esr.exe sha1=111209f78bcd004bcdd7f10732e0b03628ab6859 size=58633352 url=http://ftp.mozilla.org/pub/firefox/releases/115.16.0esr/win64/en-US/Firefox%20Setup%20115.16.0esr.exe sha256=4111e98f196f3f418223950649ad9e75a335a282f6169017440039e6dc58b238