Setting the content of a page with a special page as included template doesn't work.
Content: {{Spezial:Seiten mit ungesichteten Versionen/5,category=Begriffsklärung}}

Example HTTP-Request (reduced):
POST /w/api.php?action=edit&format=xml HTTP/1.1
Host: de.wikipedia.org
User-Agent: Mozilla/5.0
Connection: close

title=Wikipedia%3ASpielwiese&text=%7B%7BSpezial%3ASeiten%20mit%20ungesichteten%20Versionen%2F5%2Ccategory%3DBegriffskl%C3%A4rung%7D%7D&time=20081031104624&basetimestamp=20081031104503&token=123123123%2B%5C

RESPONSE:
status: 500
x-vary-options: Accept-Encoding;list-contains=gzip
connection: close

When changing one character in template name, so that it is not valid any more, the api-request succeeds.
Submitting this content via index.php also works finde.

Version: unspecified
Severity: major