Steps to replicate the issue (include links if applicable):

• run cargoQuery with |format=template in the context of special page
• (In our case, the skin parsing wikitext of mediawiki:sidebar, which using cargo_query)

What happens?:
The output (even not error, just string output), is: Parser state cleared while parsing. Did you call Parser::parse recursively? and then the trace, which by the way contains also sensitive data.

What should have happened instead?:
We can use cargo_query in context of special pages

Software version (skip for WMF-hosted wikis like Wikipedia):
1.36
Other information (browser name/version, screenshots, etc.):