The remote API in Jenkins 2.73.1 and earlier, 2.83 and earlier at /computer/(agent-name)/api showed information about tasks (typically builds) currently running on that agent. This included information about tasks that the current user otherwise has no access to, e.g. due to lack of Item/Read permission. This has been fixed, and the API now only shows information about accessible tasks.

A race condition during Jenkins 2.81 through 2.94 (inclusive); 2.89.1 startup could result in the wrong order of execution of commands during initialization. This could in rare cases result in failure to initialize the setup wizard on the first startup. This resulted in multiple security-related settings not being set to their usual strict default.

A race condition during Jenkins 2.94 and earlier; 2.89.1 and earlier startup could result in the wrong order of execution of commands during initialization. There is a very short window of time after startup during which Jenkins may no longer show the 'Please wait while Jenkins is getting ready to work' message but Cross-Site Request Forgery (CSRF) protection may not yet be effective.

Jenkins through 2.93 allows remote authenticated administrators to conduct XSS attacks via a crafted tool name in a job configuration form, as demonstrated by the JDK tool in Jenkins core and the Ant tool in the Ant plugin, aka SECURITY-624.

Jenkins before 1.586 does not set the secure flag on session cookies when run on Tomcat 7.0.41 or later, which makes it easier for remote attackers to capture cookies by intercepting their transmission within an HTTP session.

Jenkins before 1.586 does not set the HttpOnly flag in a Set-Cookie header for session cookies when run on Tomcat 7.0.41 or later, which makes it easier for remote attackers to obtain potentially sensitive information via script access to cookies.

The re-key admin monitor was introduced in Jenkins 1.498 and re-encrypted all secrets in JENKINS_HOME with a new key. It also created a backup directory with all old secrets, and the key used to encrypt them. These backups were world-readable and not removed afterwards. Jenkins now deletes the backup directory, if present. Upgrading from before 1.498 will no longer create a backup directory. Administrators relying on file access permissions in their manually created backups are advised to check them for the directory $JENKINS_HOME/jenkins.security.RekeySecretAdminMonitor/backups, and delete it if present.

The remoting module in Jenkins before 2.32 and LTS before 2.19.3 allows remote attackers to execute arbitrary code via a crafted serialized Java object, which triggers an LDAP query to a third-party server.

Jenkins before 2.3 and LTS before 1.651.2 allows remote authenticated users to trigger updating of update site metadata by leveraging a missing permissions check. NOTE: this issue can be combined with DNS cache poisoning to cause a denial of service (service disruption).

The API URL computer/(master)/api/xml in Jenkins before 2.3 and LTS before 1.651.2 allows remote authenticated users with extended read permission for the master node to obtain sensitive information about the global configuration via unspecified vectors.