Using a custom query var on a static front page results in wrong $post

[mechter]

Steps to reproduce:

• Create a page and make it the static front page
• Add a new query var via filter in theme's functions.php: add_filter( 'query_vars', function( $vars ) { array_push( $vars, 'buggy' ); return $vars; } );
• Open the front page setting the newly added query var (e.g. "​https://example.com/?buggy=yep")

Result: displays the latest blog post
Expected result: displays front page

[joyously]

I was able to reproduce this using a child theme with TwentyFifteen as the parent. TwentyFifteen does not have a front-page.php file. Also on TwentySixteen, which does not have a front-page.php either.

[bhargavbhandari90]

I am also replicating this.
Replying to joyously:

I was able to reproduce this using a child theme with TwentyFifteen as the parent. TwentyFifteen does not have a front-page.php file. Also on TwentySixteen, which does not have a front-page.php either.