Jenkins Email Extension Plugin 2.93 and earlier does not escape, sanitize, or sandbox rendered email template output or log output generated during template rendering, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers able to create or change custom email templates.

Jenkins Email Extension Plugin 2.93 and earlier does not escape various fields included in bundled email templates, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers able to control affected fields.

Email Extension Plugin 2.75 and earlier does not perform hostname validation when connecting to the configured SMTP server. This lack of validation could be abused using a man-in-the-middle attack to intercept these connections.

Email Extension Plugin 2.76 validates the SMTP hostname when connecting via TLS by default. In Email Extension Plugin 2.75 and earlier, administrators can set the Java system property mail.smtp.ssl.checkserveridentity to true on startup to enable this protection. Alternatively, this protection can be enabled (or disabled in the new version) via the 'Advanced Email Properties' field in the plugin’s configuration in Configure System.

In case of problems, this protection can be disabled again by setting mail.smtp.ssl.checkserveridentity to false using either method.

jenkins-email-ext before version 2.57.1 is vulnerable to an Information Exposure. The Email Extension Plugins is able to send emails to a dynamically created list of users based on the changelogs, like authors of SCM changes since the last successful build. This could in some cases result in emails being sent to people who have no user account in Jenkins, and in rare cases even people who were not involved in whatever project was being built, due to some mapping based on the local-part of email addresses.

An exposure of sensitive information vulnerability exists in Jenkins Email Extension Plugin 2.61 and older in src/main/resources/hudson/plugins/emailext/ExtendedEmailPublisher/global.groovy and ExtendedEmailPublisherDescriptor.java that allows attackers with control of a Jenkins administrator's web browser (e.g. malicious extension) to retrieve the configured SMTP password.