Public example files:
- https://github.githubassets.com/assets/ ... b3798e0.js
- https://www.wikipedia.org/portal/wikipe ... b9f3f0f.js
The pages where I've seen this are being served up as content-type: application/javascript.
I went back and tested various older versions -- I don't see this at all in noscript 11.2.5rc1, but see it in 11.2.5rc2 and 11.2.8 (as served up from AMO)