CMS Security Email Alert by Google
Google has recently sent out emails to webmasters running outdated versions of CMS platforms. This has likely to do with the recent increase of compromised websites which are typically tagged with “This website may harm your computer” or “This website may be compromised” statement under the title tag in the search engine results.
Example for WordPress:
Dear site owner or webmaster of [WEBSITE ADDRESS]
Your site appears to be running an older version of WordPress. Google recommends that you update to the latest release. Older or unpatched software may be vulnerable to hacking or malware that can hurt your users. To download the latest release, visit the WordPress download page.
If you have any additional questions about why you are receiving this message, Google has provided more background information in a blog post about this subject.
Google Search Quality Team