NEXTAUTH_URL set, even though it shouldn't be [NextAuth v5]

[Pirulax]

Using "next-auth": "^5.0.0-beta.28"

I spent half a day to debug an issue where (as it turns out) nextUrl was overridden.
After consulting the source code, it turns out that this piece of code is responsible for it:

next-auth/packages/next-auth/src/lib/env.ts

Lines 7 to 13 in 07b7d93

	export function reqWithEnvURL(req: NextRequest): NextRequest {
	const url = process.env.AUTH_URL ?? process.env.NEXTAUTH_URL
	if (!url) return req
	const { origin: envOrigin } = new URL(url)
	const { href, origin } = req.nextUrl
	return new NextRequest(href.replace(origin, envOrigin), req)
	}

But the thing is, I haven't set NEXTAUTH_URL anywhere, yet when I do a console.log(process.env.NEXTAUTH_URL) it's set as http://127.0.0.1:3000.
I'm running the app in a docker container, so it's a pretty isolated environment.
I've checked all my env files, compose, Dockerfile, etc, none of them set it.
Docs say it's inferred, but that inferring only works if (from what I understand anyways) NEXTAUTH_URL isn't set.

Now, after setting NEXTAUTH_URL to an empty string it works as expected, and nextUrl is not overridden anymore.

[Pirulax]

Okay, as it turns out it's apparently set somewhere in my env, but I have no clue where (yet)

Edit: Just did a reset and it seems to be ok now...