Users that are running Jenkins 2.387.3 (with its known vulnerabilities) and blue ocean must not update to snakeyaml 2.2 or they will introduce a stack trace into their Jenkins log.
The issue can be avoided by choosing to not upgrade the snakeyaml plugin to 2.2.
The issue can also be avoided by upgrading from Jenkins 2.387.3 to Jenkins 2.401.3 or Jenkins 2.414.1 and upgrading the blue ocean plugins. An updated blue ocean plugin (1.27.6) is available for Jenkins 2.401.3 with support for snakeyaml 2.2