One of the main files patched is app/core/Mage/Core/Controller/Request/Http.php
For example in Magento 1.6.2.0, doing a diff between the patched file and the original shows the following added code.
Compare: (<)V:\Magento\Magento 1.6\Changes\20150217 Patches\5346\Http.php (15698 bytes)
with: (>)V:\Magento\Magento 1.6\Changes\20150217 Patches\5346\Http.php.old (15031 bytes)
79,85d79
< * Flag for recognizing if request internally forwarded
< *
< * @var bool
< */
< protected $_internallyForwarded = false;
<
< /**
540,562d533
<
< /**
< * Define that request was forwarded internally
< *
< * @param boolean $flag
< * @return Mage_Core_Controller_Request_Http
< */
< public function setInternallyForwarded($flag = true)
< {
< $this->_internallyForwarded = (bool)$flag;
< return $this;
< }
<
< /**
< * Checks if request was forwarded internally
< *
< * @return bool
< */
< public function getInternallyForwarded()
< {
< return $this->_internallyForwarded;
< }
<
The following command line entry can quickly tell if this file has been patched by looking for the added _internallyForwarded flag. Run it in your Magento root folder:
grep "_internallyForwarded" app/code/core/Mage/Core/Controller/Request/Http.php
The following shows the file has been patched.
public_html$ grep "_internallyForwarded" app/code/core/Mage/Core/Controller/Request/Http.php
protected $_internallyForwarded = false;
$this->_internallyForwarded = (bool)$flag;
return $this->_internallyForwarded;
Other files that may have been patched:
app/code/core/Mage/Admin/Model/Observer.php
app/code/core/Mage/Core/Controller/Request/Http.php
lib/Varien/Db/Adapter/Pdo/Mysql.php
Also check app/etc/applied.patches.list to see what the latest patch applications are at the end of the list.
Watch in case Magento's totally excellent internal quality control identifies the patch as 5346 instead of 5344 as advertised on the download. They got it (something?) in the append message.