I fixed it. Just escaped the title with htmlspecialchars. See:
Index: wp-content/plugins/manageable/manageable.php
===================================================================
— wp-content/plugins/manageable/manageable.php (revision 20741)
+++ wp-content/plugins/manageable/manageable.php (working copy)
@@ -197,7 +197,7 @@
case ‘title’: ?>
<td<?php if($type == ‘page’): ?> class=”page-title”<?php endif; ?>>
<div class=”title”>
– <input type=”text” id=”title-<?php echo $post->ID ?>” value=”<?php echo $post->post_title ?>” />
+ <input type=”text” id=”title-<?php echo $post->ID ?>” value=”<?php echo htmlspecialchars($post->post_title) ?>” />
<label><?php _e(‘Slug’); ?></label><input type=”text” id=”slug-<?php echo $post->ID ?>” value=”<?php echo $post->post_name ?>” class=”slug” />
</div>
<?php if($type == ‘page’): ?>
