I work for FusionAuth. We have lambdas (basically JavaScript code that can make API calls[0] and be managed and tested[1]) that execute at fixed points in the

I work for FusionAuth. We have lambdas (basically JavaScript code that can make API calls[0] and be managed and tested[1]) that execute at fixed points in the auth lifecycle: - before a login is allowed - before a token is created - after a user returns from a federated login (SAML, OIDC, etc) - before a user registers And more[2]. And we're currently working on one for "before an MFA challenge is issued"[3]. There are some limitations[4]. We don't allow, for instance, loading of arbitrary JavaScript libraries. Not sure if that meets all your needs, but thought it was worth mentioning. 0: https://fusionauth.io/docs/extend/code/lambdas/lambda-remote-api-calls https://fusionauth.io/docs/extend/code/lambdas/lambda-remote... 1: https://fusionauth.io/docs/extend/code/lambdas/testing https://fusionauth.io/docs/extend/code/lambdas/testing 2: full list here: https://fusionauth.io/docs/extend/code/lambdas/ https://fusionauth.io/docs/extend/code/lambdas/ 3: https://github.com/FusionAuth/fusionauth-issues/issues/2309 https://github.com/FusionAuth/fusionauth-issues/issues/2309 4: https://fusionauth.io/docs/extend/code/lambdas/#limitations https://fusionauth.io/docs/extend/code/lambdas/#limitations