Some code is displaying on top of all my pages

sorry, my web page is: https://www.carlosmezo.com

I think I just got hacked, I found in header.php Lot of missplaced text or code.
Already solved!!

Hi , same problem, but I use Joomla.
Since 2013-08-28 on all my public-html webspace and there under the joomla template-folders every “index.php” have this new code inside (scroll down).
I have all lot of domains and subdomains, to change or kill this code manual is a lot of work.
So my question is:
1. Why only the index.php
2. What does this code.
3. How is this possible (Because not every joomla-folder have a domain or subdomain which can be found by searchmachine and so on, so the server must be attacked ?).
4. How can be included the code to the index.php?

Here the code which I have found in the index.php

[Code moderated. Please do not post hack code blocks in the forums.]

@carlosmezo: You need to start working your way through these resources:
https://codex.www.ads-software.com/FAQ_My_site_was_hacked
https://www.ads-software.com/support/topic/268083#post-1065779
https://smackdown.blogsblogsblogs.com/2008/06/24/how-to-completely-clean-your-hacked-wordpress-installation/
https://ottopress.com/2009/hacked-wordpress-backdoors/

Anything less will probably result in the hacker walking straight back into your site again.

Additional Resources:
Hardening WordPress
https://sitecheck.sucuri.net/scanner/
https://www.unmaskparasites.com/
https://blog.sucuri.net/2012/03/wordpress-understanding-its-true-vulnerability.html

@mznbg: Please try posting on a Joomla forum.

Hmm, my site just got attacked too. If you search Google with ’74ed9f’:

https://www.google.com.au/#q=74ed9f

This seems to be a pretty recent and widespread attack. Would really like to know how the attack is being carried out so I can make sure to prevent it happening again.

I did clean install the day before yesterday and was hit also running WP3.6. All header.php files in three different LEGAL templates.
Each of them had this extra code added:

[hacked code removed – please don’t post that here]

Google for #74ed9f# +wordpress many hits will follow. I just removed my site from internet after creating a local backup.