Tern installs software, so a flaw in it matters more than a flaw in most apps. If you find one, please tell me before telling the world.
Write to Munzzyy1@proton.me, or open a private report under the Security tab of the repository, with what you did, what happened, and the version or commit. If it is about a file Tern accepted and should not have, attach the file or say where it is published. I will answer within a few days, fix it, and credit you in the changelog unless you would rather not be named.
Please do not open a public issue for something that lets a wrong file get installed, leaks a token, or makes the app say something untrue about what is on the phone. Anything else is fine as an issue.
What Tern promises, and what it does not, is written down in docs/SECURITY-MODEL.md.