Gradle users were using the http://repo.spring.io/plugins-release repositories in plain HTTP, and not HTTPS, so a man-in-the-middle attack was possible at build time.
Maven users should at least upgrade to 6.3.0 while Gradle users should update to 6.3.1.
If you are not able to upgrade make sure not to use a Maven repository via http in your build file.
Replace all custom repository definitions in build.gradle or pom.xml with their https version.
e.g.
<repository>
<id>oss.sonatype.org-snapshot</id>
<url>https://oss.sonatype.org/content/repositories/snapshots</url> // <-- must be httpS
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
maven { url "https://repo.spring.io/plugins-release" } // <-- must be httpS
If you have any questions or comments about this advisory: