Due to changes in NGINX, there are now changes done to the default configurations which will break fastcgi sites.
NGINX in Debian, and as such, the PPAs, were previously shipping different configuration files which differed from NGINX itself. The Debian package has now synced with the nginx configurations upstream, and as such, certain very different changes have happened.
This is the massively-detailed NEWS entry in Debian for these changes:
nginx-common (1.6.1-2) unstable; urgency=medium
As of nginx-1.6.1-2 we have synced all configuration files with upstream and
we plan to keep them in sync from now on.
Unfortunately that might break existing configuration for some users. Please
check the matrix below for more information:
mime-types whitespace, changed js/rss mime type,
minor other changes & additions
scgi_params whitespace, added HTTPS
uwsgi_params whitespace, added HTTPS, removed UWSGI_SCHEME
fastcgi_params whitespace, removed SCRIPT_FILENAME
fastcgi.conf new upstream configuration file
Fastcgi configuration issues
nginx shipped a modified `fastcgi_params`, which declared `SCRIPT_FILENAME`
fastcgi_param. This line has now been removed. From now on we are also
shipping fastcgi.conf from the upstream repository, which includes a sane
`SCRIPT_FILENAME` parameter value.
So, if you are using fastcgi_params, you can try switching to fastcgi.conf
or manually set the relevant params.
You might also want to read the documentation section before proceeding.
section: $fastcgi_script_name variable.
You will need to change fastcgi_params to the fastcgi.conf file, or manually set the relevant parameters in your site configs, in order to make things work again.
(This is introduced in the PPAs as 1.6.1-2+precise0 +trusty0 and +utopic0. This is also introduced in the PPAs as 1.7.4-1+precise0 +trusty0 and +utopic0. THis will also be in Ubuntu in versions after 1.6.1-2)