recently I’ve seen ugly error pages (e.g.for 404 or 403) on my Apache 2.2 server: The supplemental text blocks have been there, but instead of header, footer and spaces “[an error occured while processing this directive]” was shown.
For these accesses, the Apache error.log showed
“unable to include potential exec ‘include/top.html’ in parsed file /usr/share/apache2/error/xyz.html.var”
as well as the same with “include/spacer.html” and “include/bottom.html”.
In my case, .html files have been configured as an executable mime type (for php). But Apache’s built-in security does not allow to include executable files (see http://issues.apache.org/bugzilla/show_bug.cgi?id=32346 to change that).
Since I considered php code within .html files useless for me, did not apply the patch and erased the .html and .htm entries from the corresponding “AddType” entry in httpd.conf.