"Show Full Post" button doesn't work in subfolder installations

Falco · December 18, 2025, 7:36pm

Thanks to @Thiago_Mobilon I’ve found the issue and have a proposed fix

github.com/discourse/discourse

FIX: FinalDestination ignoring all URLs on domain for subfolder installs

main ← fix-final-destination-subfolder-ignore

merged 01:52PM - 23 Dec 25 UTC

xfalcox

+56 -5

For subfolder installs (e.g. `example.com/forum`), `FinalDestination` was ignori…ng all URLs on the parent domain instead of just URLs under the subfolder path. ### Problem When Discourse is installed in a subfolder like `https://tecnoblog.net/comunidade/`, attempting to onebox/fetch URLs like `https://tecnoblog.net/noticias/...` (WordPress blog on same domain) would fail because FinalDestination immediately returned without making any HTTP request. ### Cause - `Discourse.base_url_no_prefix` returns just `https://tecnoblog.net` (no path) - Only hostnames were stored in the ignored list - Any URL on `tecnoblog.net` matched and was ignored ### Fix - Use `Discourse.base_url` which includes the subfolder path - Store both hostname and path in the ignored list - Check both hostname AND path prefix when determining if a URL should be ignored ### Security SSRF protection is unaffected - it runs after the ignored check, so URLs that are no longer ignored still go through IP validation. Added a test to verify this.

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"Show Full Post" button doesn't work in subfolder installations

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