This blog post can make WordPress crash

Was writing a blog post today. Happy, typing away. Hit Preview, and bam:

Service Temporarily Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Say wahaat? Strange thing was my website was otherwise working normally. Could even edit other posts just fine!

Some head scratching, googling and making a support request to Dreamhost followed. Apparently they had just had an outtake, so I figured it might be related. They did too. But it was not! I finally found the answer on a blog:

Turns out this error is not alone in WordPress and not a bug of it at all. Some of the administration tasks of other CMS software such as posting posts with PHP code in them and uploading stuff would also trigger a module in Apache called Mod_security to be over sensitive. -- www.kavoir.com

And sure enough, I had mentioned a PHP function called curl_exec in my blog post. Once I removed that word, the post could be previewed and saved just fine. Great stuff...

Solution

Of course I could just have avoided using that word, but that's no fun. After reading the rest of that mentioned blog post, some comments and wiki page at Dreamhost, I found that by adding the lines below to the .htaccess file the problem was fixed. Or makes it go away at least 😛

<IfModule mod_security.c>
  SetEnvIfNoCase Request_URI ^/wp-admin/(?:post|async-upload)\.php$ MODSEC_ENABLE=Off
  SetEnvIfNoCase Request_URI ^/xmlrpc\.php$ MODSEC_ENABLE=Off
  SecFilterDebugLevel 0
  SecFilterDefaultAction "deny,nolog,noauditlog,status:503"
</IfModule>

Alrighty... back to my actual blog post...