A recent change is breaking the Echo-Notfication-List and the hovercard extension, probably other scripts too.
It is caused by blocked calls to https://bits.wikimedia.org/event.gif? (blocked e.g. by Firefox with Adblock Plus).
>>! In T86900#979360, @Se4598 wrote:
> On leaving the hovercard a request is created (and appears as blocked in Adblock Plus), simultaneously Web Console gets a red x entry with message ":" only and location (via debug=true) at ext.eventLogging.core.js:222 (1.25wmf14) in the EventLogging-Extension.
I suspect this is caused by https://gerrit.wikimedia.org/r/182890 (which was also backported to wmf13 and 14)