I encountered an issue attempting to upgrade to the latest version via the Joomla Extensions:Update process: "Update path does not exist." This error seems to happen frequently with T3 updates. I was, however, able to install the new version manually.
I was reviewing the updates in the latest version (2.5.5) and noticed line 47 in the base-bs3\html\com_content\article\default.php file includes this code:
<pre class="line-numbers"><code class="language-markup"> <meta itemscope itemprop="mainEntityOfPage" itemType="https://schema.org/WebPage" itemid="https://google.com/article"/></code></pre>
According to W3,
"The itemid attribute, if specified, must have a value that is a valid URL potentially surrounded by spaces."Although the Google page on structured data includes an itemid of "https://google.com/article" it appears to be purely an example since that URL is not valid.
Also, the "inLanguage" meta tag on line 48 is missing the itemscope parameter that would specify that the Article is the scope for the inLanguage value. Without the itemscope parameter, the inLanguage parameter is applied to the entire WebPage (which suggests it should be added to the <head> section rather than the <article>
. 
