Apply url_preview_url_blacklist to oEmbed and pre-cached images (#15601)

There are two situations which were previously not properly checked:

1. If the requested URL was replaced with an oEmbed URL, then the
   oEmbed URL was not checked against url_preview_url_blacklist.
2. Follow-up URLs (either via autodiscovery of oEmbed or to pre-cache
   images) were not checked against url_preview_url_blacklist.

1 files changed, 1 insertions, 0 deletions

diff --git a/changelog.d/15601.bugfix b/changelog.d/15601.bugfix
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+Fix a long-standing bug where the `url_preview_url_blacklist` configuration setting was not applied to oEmbed or image URLs found while previewing a URL.