Error saving formatted content in EPP 5.2 SitePublisher

Issue

Saving content with some advanced formatting applied fails with the following error:

ERROR [portal:UIPortalApplication] Error during the processAction phase
java.lang.NoClassDefFoundError: org/w3c/css/sac/DocumentHandler
        at org.owasp.validator.html.scan.AntiSamyDOMScanner.recursiveValidateTag(AntiSamyDOMScanner.java:586)
        at org.owasp.validator.html.scan.AntiSamyDOMScanner.scan(AntiSamyDOMScanner.java:193)


Caused by: java.lang.ClassNotFoundException: org.w3c.css.sac.DocumentHandler from BaseClassLoader@5e086a0f{vfsfile:gatein-wcm-extension-5.2.0-exo-2.3.3-CP01.ear/}
        at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:477)