It could be caused by this OpenSearch code that we have in all of our pages:
<link href="/static/search_plugins/opensearch/musicbrainz_artist.xml" rel="search" title="MusicBrainz: Artist" type="application/opensearchdescription+xml"/>
<link href="/static/search_plugins/opensearch/musicbrainz_label.xml" rel="search" title="MusicBrainz: Label" type="application/opensearchdescription+xml"/>
<link href="/static/search_plugins/opensearch/musicbrainz_release.xml" rel="search" title="MusicBrainz: Release" type="application/opensearchdescription+xml"/>
<link href="/static/search_plugins/opensearch/musicbrainz_track.xml" rel="search" title="MusicBrainz: Track" type="application/opensearchdescription+xml"/>
With Firefox, when you browse MusicBrainz, you can click the ellipsis (…) icon in the address bar to add one of these searches (MusicBrainz: Artist/Release/Track, but I don’t know why, MusicBrainz: Label does not show up).
With Vivaldi, nothing happens.
Maybe Chrome automatically stores all OpenSearches it sees when you browse?
If you use DuckDuckGo search engine, you don’t need to build or to add each of those searches, you can simply use DuckDuckGo MusicBrainz !bangs.