MikroTIk and Heartbleed, the official explanation:
All RouterOS versions are secure against the Heartbleed issue.
All versions prior to v6.12 used an unaffected, older version of OpenSSL, and since v6.12 the latest OpenSSL version will be used, where the heartbleed issue is already fixed.
We didn’t use any of the affected OpenSSL versions in any of our products, so no specific action is required on your side.
v2 until v6.11 (included) = secure because use an older OpenSSL version
v6.12 (and above) = secure because use a newer OpenSSL version