Inconsistent state in UI after boards permission change by system admin

Mattermost fails to properly show information in the UI, allowing a system admin to modify a board state allowing any user with a valid sharing link to join the board with editor access, without the UI showing the updated permissions.

Disabling publicly-shared boards does not disable existing publicly available board links

Mattermost fails to disable public Boards after the "Enable Publicly-Shared Boards" configuration option is disabled, resulting in previously-shared public Boards to remain accessible.

channel DoS by sharing a boards link

Mattermost Boards fail to properly validate a board link, allowing an attacker to crash a channel by posting a specially crafted boards link.

Member can create team with team override scheme

Mattermost fails to properly check the authorization of POST /api/v4/teams when passing a team override scheme ID in the request, allowing an authenticated attacker with knowledge of a Team Override Scheme ID to create a new team with said team override scheme.

Lack of channel membership check when linking a board to a channel

Mattermost fails to verify channel membership when linking a board to a channel allowing a low-privileged authenticated user to link a Board to a private channel they don't have access to, 

WebSockets accept connections from HTTPS origin

Mattermost fails to properly validate the origin of a websocket connection allowing a MITM attacker on Mattermost to access the websocket APIs.

Limited blind SSRF to localhost/intranet in interactive dialog implementation

Mattermost fails to properly restrict requests to localhost/intranet during the interactive dialog, which could allow an attacker to perform a limited blind SSRF.

Mattermost 6.0 and earlier fails to sufficiently validate parameters during post creation, which allows authenticated attackers to cause a client-side crash of the web application via a maliciously crafted post.

Mattermost 6.0 and earlier fails to sufficiently validate the email address during registration, which allows attackers to trick users into signing up using attacker-controlled email addresses via crafted invitation token.

Mattermost 6.0.2 and earlier fails to sufficiently sanitize user's password in audit logs when user creation fails.

Mattermost 5.38 and earlier fails to sufficiently sanitize clipboard contents, which allows a user-assisted attacker to inject arbitrary web script in product deployments that explicitly disable the default CSP.

Reflected XSS in OAuth Flow

Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.

An issue was discovered in Mattermost Server before 5.19.0, 5.18.1, 5.17.3, 5.16.5, and 5.9.8. Creation of a trusted OAuth application does not always require admin privileges, aka MMSA-2020-0001.

An issue was discovered in Mattermost Server before 5.19.0. Attackers can rename a channel and cause a collision with a direct message, aka MMSA-2020-0002.

An issue was discovered in Mattermost Server before 5.19.0. Attackers can discover private channels via the "get channel by name" API, aka MMSA-2020-0004.

An issue was discovered in Mattermost Server before 5.20.0. Non-members can receive broadcasted team details via the update_team WebSocket event, aka MMSA-2020-0012.

An issue was discovered in Mattermost Desktop App before 4.4.0. The Same Origin Policy is mishandled during access-control decisions for web APIs, aka MMSA-2020-0006.

An issue was discovered in Mattermost Desktop App before 4.4.0. Prompting for HTTP Basic Authentication is mishandled, allowing phishing, aka MMSA-2020-0007.

An issue was discovered in Mattermost Desktop App before 4.4.0. Attackers can open web pages in the desktop application because server redirection is mishandled, aka MMSA-2020-0008.

An issue was discovered in Mattermost Server before 5.21.0. Socket read operations are not appropriately restricted, which allows attackers to cause a denial of service, aka MMSA-2020-0005.