DEB packages of mediawiki and many of its extensions, are prepared as part of the WP-MIRROR project.
During the build process, lintian performs a great number of sanity checks, including seeing if each file has file permissions appropriate to its file type.
When lintian sees a non-executable file with 755 permissions, rather than 644, lintian will throw a warning like:
W: wp-mirror-mediawiki: executable-not-elf-or-script usr/share/wp-mirror-mediawiki/skins/Blueprint/lib/bootstrap/bootstrap.min.css.
2) Files which should have permissions set to 644
3) Technical details
DEB standards version: 3.9.6
GIT branch: master