We've just published a new version (3.0.3.RELEASE) of the thymeleaf-extras-springsecurity3 and thymeleaf-extras-springsecurity4 integration packages. These are bugfixing versions that should be usable as drop-in replacements of the previous 3.0.x versions.
But also, for the first time, a new thymeleaf-extras-springsecurity5 has been published too (same "3.0.3.RELEASE" version), including support for Spring Security 5 in both Spring MVC and Spring WebFlux applications. This Spring Security 5 support allows the use of Spring Security integrations in WebFlux applications in a non-blocking manner thanks to new support added in the just-published version 3.0.10 of the Thymeleaf core.
See it at our ecosystem page: http://www.thymeleaf.org/ecosystem.html#thymeleaf-spring-security
Or go directly to the project's page on GitHub: https://github.com/thymeleaf/thymeleaf-extras-springsecurity
Remember our website includes an article (+ example application) "Thymeleaf + Spring Security integration basics". Check it out here: http://www.thymeleaf.org/doc/articles/springsecurity.html
And also, if you like to experiment a bit, we have two sandbox applications based on Spring Boot 2.1 (current snapshot) with Spring Security 5:
Regards,
Daniel