Discourse is a platform for community discussion. Users who receive an invitation link that is not scoped to a single email address can enter any non-admin user's email and gain access to their account when accepting the invitation. All users should upgrade to the latest version. A workaround is temporarily disabling invitations with SiteSetting.maxinvitesperday = 0 or scope them to individual email addresses.

Discourse is an open source platform for community discussion. Versions prior to 2.8.13 (stable), 3.0.0.beta16 (beta) and 3.0.0beta16 (tests-passed), are vulnerable to cross-site Scripting. A maliciously crafted URL can be included in a post to carry out cross-site scripting attacks on sites with disabled or overly permissive CSP (Content Security Policy). Discourse's default CSP prevents this vulnerability. This vulnerability is patched in versions 2.8.13 (stable), 3.0.0.beta16 (beta) and 3.0.0beta16 (tests-passed). As a workaround, enable and/or restore your site's CSP to the default one provided with Discourse.

Discourse is an open-source discussion platform. Prior to version 3.0.1 on the stable branch and version 3.1.0.beta2 on the beta and tests-passed branches, a malicious user can cause a regular expression denial of service using a carefully crafted user agent. This issue is patched in version 3.0.1 on the stable branch and version 3.1.0.beta2 on the beta and tests-passed branches. There are no known workarounds.

Discourse is an option source discussion platform. Prior to version 2.8.14 on the stable branch and version 3.0.0.beta16 on the beta and tests-passed branches, when a user requests for a password reset link email, then changes their primary email, the old reset email is still valid. When the old reset email is used to reset the password, the Discourse account's primary email would be re-linked to the old email. If the old email address is compromised or has transferred ownership, this leads to an account takeover. This is however mitigated by the SiteSetting emailtokenvalidhours which is currently 48 hours. Users should upgrade to versions 2.8.14 or 3.0.0.beta15 to receive a patch. As a workaround, lower emailtokenvalidhours as needed.

Discourse is an option source discussion platform. Prior to version 2.8.14 on the stable branch and version 3.0.0.beta16 on the beta and tests-passed branches, pending post titles can be used for cross-site scripting attacks. Pending posts can be created by unprivileged users when a category has the "require moderator approval of all new topics" setting set. This vulnerability can lead to a full XSS on sites which have modified or disabled Discourse’s default Content Security Policy. A patch is available in versions 2.8.14 and 3.0.0.beta16.

Discourse is a platform for community discussion. A malicious admin could use this vulnerability to perform port enumeration on the local host or other hosts on the internal network, as well as against hosts on the Internet. Latest stable, beta, and test-passed versions are now patched. As a workaround, self-hosters can use DISCOURSEBLOCKEDIPBLOCKS env var (which overrides blockedipblocks setting) to stop webhooks from accessing private IPs.

Discourse is an open source discussion platform. Prior to version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches, in multiple controller actions, Discourse accepts limit params but does not impose any upper bound on the values being accepted. Without an upper bound, the software may allow arbitrary users to generate DB queries which may end up exhausting the resources on the server. The issue is patched in version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches. There are no known workarounds for this vulnerability.

Discourse is an open-source messaging platform. In versions 2.8.10 and prior on the stable branch and versions 2.9.0.beta11 and prior on the beta and tests-passed branches, users composing malicious messages and navigating to drafts page could self-XSS. This vulnerability can lead to a full XSS on sites which have modified or disabled Discourse’s default Content Security Policy. This issue is patched in the latest stable, beta and tests-passed versions of Discourse.

Discourse is an open source discussion platform. Prior to version 3.1.0.beta7 of the beta and tests-passed branches, a CSP (Content Security Policy) nonce reuse vulnerability was discovered could allow cross-site scripting (XSS) attacks to bypass CSP protection for anonymous (i.e. unauthenticated) users. There are no known XSS vectors at the moment, but should one be discovered, this vulnerability would allow the XSS attack to bypass CSP and execute successfully. This vulnerability isn't applicable to logged-in users. Version 3.1.0.beta7 contains a patch. The stable branch doesn't have this vulnerability. A workaround to prevent the vulnerability is to disable Google Tag Manager, i.e., unset the gtm container id setting.

Discourse is an option source discussion platform. Prior to version 2.8.14 on the stable branch and version 3.0.0.beta16 on the beta and tests-passed branches, tag descriptions, which can be updated by moderators, can be used for cross-site scripting attacks. This vulnerability can lead to a full XSS on sites which have modified or disabled Discourse’s default Content Security Policy. Versions 2.8.14 and 3.0.0.beta16 contain a patch.

Discourse is an open-source discussion platform. Prior to version 3.1.1 of the stable branch and version 3.2.0.beta1 of the beta and tests-passed branches, a malicious admin could create extremely large icons sprites, which would then be cached in each server process. This may cause server processes to be killed and lead to downtime. The issue is patched in version 3.1.1 of the stable branch and version 3.2.0.beta1 of the beta and tests-passed branches. This is only a concern for multisite installations. No action is required when the admins are trusted.

Discourse is an open-source discussion platform. Prior to version 3.1.1 of the stable branch and version 3.2.0.beta1 of the beta and tests-passed branches, a malicious user could add a 2FA or security key with a carefully crafted name to their account and cause a denial of service for other users. The issue is patched in version 3.1.1 of the stable branch and version 3.2.0.beta1 of the beta and tests-passed branches. There are no known workarounds.

Discourse is an open-source discussion platform. Prior to version 3.1.1 of the stable branch and version 3.2.0.beta1 of the beta and tests-passed branches, importing a remote theme loads their assets into memory without enforcing limits for file size or number of files. The issue is patched in version 3.1.1 of the stable branch and version 3.2.0.beta1 of the beta and tests-passed branches. There are no known workarounds.

Discourse is an open source discussion platform. Prior to version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches, a malicious user can prevent the defer queue from proceeding promptly on sites hosted in the same multisite installation. The issue is patched in version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches. There are no known workarounds for this vulnerability. Users of multisite configurations should upgrade.

Discourse is the an open source discussion platform. In some rare cases users redeeming an invitation can be added as a participant to several private message topics that they should not be added to. They are not notified of this, it happens transparently in the background. This issue has been resolved in commit a414520742 and will be included in future releases. Users are advised to upgrade. Users are also advised to set SiteSetting.maxinvitesperday to 0 until the patch is installed.

Discourse is an option source discussion platform. Prior to version 2.8.14 on the stable branch and version 2.9.0.beta16 on the beta and tests-passed branches, parsing posts can be susceptible to regular expression denial of service (ReDoS) attacks. This issue is patched in versions 2.8.14 and 2.9.0.beta16. There are no known workarounds.

Discourse is an option source discussion platform. Prior to version 2.8.14 on the stable branch and version 2.9.0.beta16 on the beta and tests-passed branches, users can create posts with raw body longer than the maxlength site setting by including html comments that are not counted toward the character limit. This issue is patched in versions 2.8.14 and 2.9.0.beta16. There are no known workarounds.

In version 2.9.0.beta14 of Discourse, an open-source discussion platform, maliciously embedded urls can leak an admin's digest of recent topics, possibly exposing private information. A patch is available for version 2.9.0.beta15. There are no known workarounds for this issue.

Discourse is an option source discussion platform. Prior to version 2.8.14 on the stable branch and version 3.0.0.beta16 on the beta and tests-passed branches, the number of times a user posted in an arbitrary topic is exposed to unauthorized users through the /u/username.json endpoint. The issue is patched in version 2.8.14 and 3.0.0.beta16. There is no known workaround.

Discourse is an open-source discussion platform. Prior to version 3.0.1 on the stable branch and version 3.1.0.beta2 on the beta and tests-passed branches, someone can use the excludetag param to filter out topics and deduce which ones were using a specific hidden tag. This affects any Discourse site using hidden tags in public categories. This issue is patched in version 3.0.1 on the stable branch and version 3.1.0.beta2 on the beta and tests-passed branches. As a workaround, secure any categories that are using hidden tags, change any existing hidden tags to not include private data, or remove any hidden tags currently in use.

Discourse is an open-source discussion platform. Prior to version 3.0.1 on the stable branch and 3.1.0.beta2 on the beta and tests-passed branches, the contents of latest/top routes for restricted tags can be accessed by unauthorized users. This issue is patched in version 3.0.1 on the stable branch and 3.1.0.beta2 on the beta and tests-passed branches. There are no known workarounds.

Discourse is an open source discussion platform. The embeddable comments can be exploited to create new topics as any user but without any clear title or content. This issue is patched in the latest stable, beta and tests-passed versions of Discourse. As a workaround, disable embeddable comments by deleting all embeddable hosts.

Discourse is an open-source discussion platform. Prior to versions 3.4.3 on the stable branch and 3.5.0.beta3 on the beta branch, the users limit for a DM can be bypassed, thus giving the ability to potentially create a DM with every user from a site in it. This issue has been patched in stable version 3.4.3 and beta version 3.5.0.beta3.

Discourse is an open source discussion platform. Prior to version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches, information about restricted-visibility topic tags could be obtained by unauthorized users. The issue is patched in version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches.

Discourse is an open source discussion platform. Prior to version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches, a malicious user can edit a post in a topic and cause a DoS with a carefully crafted edit reason. The issue is patched in version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches. There are no known workarounds for this vulnerability.

Discourse is an open-source discussion platform. Prior to version 2.8.13 of the stable branch and version 2.9.0.beta14 of the beta and tests-passed branches, unauthorized users may learn of the existence of hidden tags and that they have been applied to topics that they have access to. This issue is patched in version 2.8.13 of the stable branch and version 2.9.0.beta14 of the beta and tests-passed branches. As a workaround, use the disableemail site setting to disable all emails to non-staff users.

Discourse is an open-source discussion platform. In version 2.8.13 and prior on the stable branch and version 2.9.0.beta14 and prior on the beta and tests-passed branches, any authenticated user can create an unlisted topic. These topics, which are not readily available to other users, can take up unnecessary site resources. A patch for this issue is available in the main branch of Discourse. There are no known workarounds available.

Discourse is an open-source discussion platform. Prior to version 3.0.1 on the stable branch and 3.1.0.beta2 on the beta and tests-passed branches, when submitting a membership request, there is no character limit for the reason provided with the request. This could potentially allow a user to flood the database with a large amount of data. However it is unlikely this could be used as part of a DoS attack, as the paths reading back the reasons are only available to administrators. Starting in version 3.0.1 on the stable branch and 3.1.0.beta2 on the beta and tests-passed branches, a limit of 280 characters has been introduced for membership requests.

Discourse is an open-source discussion platform. Prior to version 3.0.1 of the stable branch and version 3.1.0.beta2 of the beta and tests-passed branches, the count of topics displayed for a tag is a count of all regular topics regardless of whether the topic is in a read restricted category or not. As a result, any users can technically poll a sensitive tag to determine if a new topic is created in a category which the user does not have excess to.

In version 3.0.1 of the stable branch and version 3.1.0.beta2 of the beta and tests-passed branches, the count of topics displayed for a tag defaults to only counting regular topics which are not in read restricted categories. Staff users will continue to see a count of all topics regardless of the topic's category read restrictions.

Discourse is an open-source messaging platform. In versions 3.0.1 and prior on the stable branch and versions 3.1.0.beta2 and prior on the beta and tests-passed branches, the count of personal messages displayed for a tag is a count of all personal messages regardless of whether the personal message is visible to a given user. As a result, any users can technically poll a sensitive tag to determine if a new personal message is created even if the user does not have access to the personal message.

In the patched versions, the count of personal messages tagged with a given tag is hidden by default. To revert to the old behaviour of displaying the count of personal messages for a given tag, an admin may enable the displaypersonalmessagestagcounts site setting.