Case-sensitive host header lookup in fetch redirect breaks cross-origin requests with custom headers

[rahulrao85]

Description

In fetch.ts (line 464), the redirect host header update uses a case-sensitive key lookup:

if (headers['host'])
    headers['host'] = locationURL.host;

This is inconsistent with the rest of the file, where every other header operation uses case-insensitive lookup:

• setHeader() (line 935): uses Object.entries().find(pair => pair[0].toLowerCase() === name.toLowerCase())
• getHeader() (line 943): same
• removeHeader() (line 948): same

If extraHTTPHeaders or any other header source sets 'Host' (capital H), headers['host'] (lowercase) returns undefined, and the host header is never updated for the redirect target. The redirect request retains the original host header unmodified.

Impact

• Redirects from https://example.com/page to https://api.example.com/data will send Host: example.com instead of Host: api.example.com
• This causes connection failures or incorrect routing for any cross-origin redirect where the Host header was set with non-lowercase casing
• Particularly impacts users who set custom extraHTTPHeaders via browserContext.setExtraHTTPHeaders()
• The fix is a one-line change

Suggested Fix

const hostKey = Object.keys(headers).find(k => k.toLowerCase() === 'host');
if (hostKey)
    headers[hostKey] = locationURL.host;

This matches the pattern used by setHeader, getHeader, and removeHeader in the same file.