SUPEE-6788

[Schrank]

In case you need to maintain this no longer maintained extension:

Create your own extension, use following code to whitelist cms blocks in emails.

<?php
/** @var $installer Mage_Catalog_Model_Resource_Setup */
$installer = $this;
$installer->startSetup();

// Make sure the upgrade is not performed on legacy installations with tables missing
$adminVersion = Mage::getConfig()->getModuleConfig('Mage_Admin')->version;
if (version_compare($adminVersion, '1.6.1.1', '>')) {
    $connection = $installer->getConnection();
    //---------------------------------------------------
    // Add blocks
    //---------------------------------------------------
    $table = $installer->getTable('admin/permission_block');
    if ($table) {
        $blockNames = array(
            "cms/block",
            "germansetup/imprint_field",
            "germansetup/imprint_content",
        );

        foreach ($blockNames as $blockName) {
            $connection->insertIgnore(
                $table,
                array(
                    'block_name' => $blockName,
                    'is_allowed' => 1,
                )
            );
        }
    }
}
$installer->endSetup();