On Dec 31, 2015 version 2.2 of this add-on was released to address an exploitable SQL injection vulnerability. If you are still using a version of this add-on which is below 2.2 or released before Dec 31, 2015 then it is essential that you update to the latest version of the add-on as soon as possible to fix this security issue.
Email Subscription v3.0 changes:
1) Emails are sent only if there are new threads.
2) Phrase updated.
Email Subscription v2.9 changes:
Previous version (v2.8) had a problem with the PHP file and was not sending out emails on some servers. Please upgrade to v2.9.
Email Subscription v2.8 changes:
Now emails are mobile phone friendly. Added Image URL option.
Email Subscription v2.7 changes:
Censoring function now honored. Thread titles and links now censored in the email being sent.
Admin Control Panel -> Options -> Censoring -> Words to Censor
Email Subscription v2.6 changes:
Added code to bypass sending emails if there are no new threads.
Email Subscription v2.5 changes:
Added ability to delete a subscription from the Admin page.