To reproduce:
- Go to https://en.wikipedia.org/wiki/Special:ExpandTemplates?useskin=cologneblue
- Fill in content title = Main Page, input wikitext = {{ambox}}
- Click OK button
- The template is rendered, but with the default skin. Sometimes the whole point is to preview how something looks under different skins.
Environment: live enwiki, which is apparently
- MediaWiki 1.31.0-wmf.21 (rMW828e6ccf0542)
- HHVM 3.18.6-dev (srv)
- MariaDB 10.0.32-MariaDB