The only version being kept up-to-date is the one on master branch, i.e. the one regularly being deployed to https://cassette-app.de. Although self-hosting is possible no further effort is taken to patch specific versions as there is no actual, strict versioning anyway.

In case you found an (assumed) security vulnerability please contact me directly at me(youknowit)fdlo.ch instead of opening an issue. We will work it out then ;).