What are the ethical considerations when publishing a cheating technique?
I can’t really tell you what to do with that vague level of detail, but I can give you an example.

There seems to be a team at the Ben-Gurion University in Israel that regularly comes up with obscure ways to transmit data to devices not connected via any network connection.

Stuff like:


DiskFiltration: Data Exfiltration from Speakerless Air-Gapped Computers via Covert Hard Drive Noise,
SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit,
and many many more.


The only uses I see for that stuff is to either help malware authors and intelligence agencies or make people aware of this communication channels to increase security.

If your findings are anything like this, I don’t see a problem.

Update
After you clarified it's about a method to remotely stream answers of a test directly into the retina without anyone else noticing:

There are a lot of uses for such a technique which are not related to cheating. Pick some of them as motivation, and then later in your paper describe how this could also be used for cheating. Maybe give hints what some mitigation measures could be.