Failing to parse set-cookie headers when run from Zotero

[diegodlh]

• wikibase-edit version: 4.11.8
• Environment: browser version

I'm developing a plugin for Zotero, which runs on Firefox runtime environment.

Wikidata is returning multiple set-cookie headers, and cross-fetch is failing to parse them because of the way Firefox's XMLHttpRequest.prototype.getAllResponseHeaders() is concatenating them.

I have posted JakeChampion/fetch#928 (cross-fetch depends on github/fetch), but I thought of posting an issue here as well, to keep track of it.

For the moment, applying the patch attached to cross-fetch fixes the issue (added .txt file extension at the end so Github would let me attach it).
cross-fetch+3.0.6 .patch.txt