Data Spillage Handling¶

Available on Entry and Enterprise Advanced plans

Data Spillage Handling helps prevent accidental data spillage and helps system administrators respond quickly to potential leaks without disrupting collaboration. Enabling this feature empowers Mattermost users to report messages that may contain sensitive, regulated, or inappropriate information, and enables designated content reviewers to assess and take appropriate action by removing or dismissing quarantined messages.

By making every team member a first line of defense against sensitive-data exposure, Data Spillage Handling strengthens mission-critical, secure deployments and supports compliance with organizational and regulatory data-handling standards.

Before you begin¶

You must be a System Admin in Mattermost. You need to identify who will be content reviewers for quarantined messages, and you need to decide whether quarantined messages should be hidden from users in Mattermost while under review.

Enable¶

Data Spillage Handling isn’t enabled by default. To enable Data Spillage Handling:

Go to System Console > Site Configuration > Data Spillage Handling.
Set Enable Data Spillage Handling to True.

Alternatively, you can configure Data Spillage Handling via the config.json file or through environment variables.

Configure¶

Under Content Reviewers, define who should review quarantined content:
- Same reviewers for all teams: Set to True to apply one global reviewer list across all teams, or False to configure reviewers per team.
- Reviewers: Start typing to search for users to assign as content reviewers.
Important

Choose reviewers carefully. Assigning reviewer roles grants access to potentially sensitive information and may expose data from private channels.
- A global reviewer can view quarantined messages from all teams and channels, including private channels they’re not a member of.
- Team-specific reviewers can view quarantined messages from their assigned teams, including private channels within those teams they’re not members of.
- Additional reviewers: Optionally include:
  - System Administrators: System admins receive quarantined messages for all teams they are part of.
  - Team Administrators: Team admins receive quarantined messages for their respective teams.
Under Notification Settings, specify who receives updates at each stage of the quarantine workflow when content is quarantined or reviewed:
- Notify when content is quarantined: Reviewer(s), Author.
- Notify when a reviewer is assigned: Reviewer(s).
- Notify when content is removed: Reviewer(s), Author, Reporter.
- Notify on dismissal: Reviewer(s), Author, Reporter.
All notifications are sent via the Data Spillage Bot as direct messages.
Under Additional Settings, configure how the quarantine workflow behaves:
- Reasons for quarantine: Define the preset categories that appear in the quarantine dialog for users (for example: Classification mismatch, Need-to-know violation, Personally identifiable information (PII) exposure, Operational security (OPSEC) concern, Controlled Unclassified Information (CUI) violation).
- Require reporters to add comment: Set to True to require users to add a short explanation when quarantining a message.
- Require reviewers to add comment: Set to True to require reviewers to add a comment when resolving a quarantine.
- Hide message from channel while it is being reviewed: Set to True to automatically hide quarantined messages from the channel until reviews are complete. If a root post is quarantined, the entire thread is hidden.

Tip

We recommend enabling Hide message from channel while it is being reviewed and require comments from both reporters and reviewers to maintain transparency, accountability, and an auditable record of actions.

Monitor quarantined messages¶

When a user quarantines a message, the Data Spillage Bot sends a direct message to all content reviewers.

Direct messages from the Data Spillage Bot is a centralized moderation queue, where reviewers can view, assign, and act on quarantined messages without leaving Mattermost. Reviewers can use it to monitor potential data spills, coordinate response, and maintain an auditable record of review activity.

Each quarantined message appears as a card-formatted message that includes:

Quarantined by: The user who reported the message.
Status: The current state of the review. All quarantined content starts in Pending status.
Reason: The reason selected by the reporter (for example, Classification mismatch, Need-to-know violation).
Message preview: A snippet of the quarantined message, including the author, timestamp, and original channel.
Reviewer: The user currently assigned to review the message (initially Unassigned).
Channel: The name of the channel where the message was originally posted.
Team: The team context for the quarantined message.
Comment: Any reporter-provided context.
Post ID: The system identifier for the original message for auditing purposes.

Reviewers can select View details to take action as follows:

Assign a Reviewer responsible for reviewing the quarantined message.
Remove message: Permanently delete the quarantined message from its original channel for all users. The status of the quarantined message changes to Removed.
Keep message: Dismiss the quarantine and restore the message if it was hidden. The status of the quarantined message changes to Retained.
Add a comment: Record the reason for the decision when required.
Generate a report: Download a report of the quarantined message and review activity for record-keeping or incident response. See Generate a quarantined message report for details.

Once an action is taken, the Status field updates automatically. The Data Spillage Bot sends follow-up notifications to the reporter, author, and other reviewers based on how Data Spillage Handling is configured.

Generate a quarantined message report¶

Reviewers can generate a downloadable report that captures the full context of a quarantined message and the associated review activity. Reports are useful for record-keeping, incident response, and preserving evidence before a message is permanently removed.

A report can be generated from any of the following entry points:

From the quarantined message details: Select Download report from the message details panel. This option is available regardless of the quarantine’s status, including Pending, Reviewer Assigned, Removed, or Retained.
From the Remove message flow: When you select Remove message, the confirmation dialog includes a Download quarantined message report checkbox, selected by default. With the checkbox selected, Mattermost generates and downloads the report before you can permanently remove the message. This safeguard ensures the record is preserved on your device before the message contents are deleted.
From the Keep message flow: When you select Keep message, the confirmation dialog includes the same checkbox. With the checkbox selected, Mattermost generates and downloads the report in the background while the keep action completes.

If you choose to skip the report download from the Remove message or Keep message flow, Mattermost asks you to confirm that you’re proceeding without a report. The skip decision is recorded in the audit log.

If report generation fails (for example, due to a network interruption or session timeout), the dialog displays an error and offers a retry option. You can also skip the report and proceed with the action, or cancel and download the report later from the message details.

Each time a reviewer generates a report, the Data Spillage Bot notifies all content reviewers so an auditable record exists whenever a copy of the potentially spilled data is obtained.

Tip

We recommend generating a report before removing a message. Once a message is removed, its content, attachments, and edit history are permanently deleted and can’t be recovered.

Report contents and format¶

Each report is a ZIP archive containing YAML metadata files and the original file attachments. YAML is used because it’s both human-readable and machine-parseable, which makes the report suitable for manual review and for ingestion by downstream compliance or incident-response tooling.

The archive has the following structure:

/
├── report_metadata.yaml
├── content_review.yaml
├── post/
│   ├── post.yaml
│   └── attachments/
│       └── <original attachment files>
└── edit_history/
    └── <edit_post_id>/
        ├── post.yaml
        └── attachments/
            └── <original attachment files>

report_metadata.yaml: Identifies the report itself, including the user ID and username of the reviewer who generated the report, the generation timestamp, and the report format version (used for forward compatibility if the report format changes in future releases).
content_review.yaml: Captures the data spillage event, including the reporter’s user ID, username, selected reason, and comment; the report timestamp; whether the message was hidden during review; and, once the quarantine is resolved, the reviewer’s user ID, username, comment, and action timestamp. For unresolved quarantines, reviewer fields are omitted.
post/post.yaml: Describes the quarantined message, including the post ID, author ID, author name, author email, message content, channel ID, channel display name, team ID, team display name, creation and update timestamps, pinned status, root ID, post properties, post metadata, reply count (for root posts), and the ordered list of edit history post IDs.
post/attachments/: The original files attached to the quarantined message, included verbatim.
edit_history/<edit_post_id>/: One subdirectory per previous version of the message, each containing a post.yaml and an attachments/ directory in the same format as the base post directory.

To avoid duplication, attachment files are deduplicated across the entire archive by their file ID. Each unique attachment appears exactly once — under the base post if it exists in the current version of the message, or under the earliest edit-history entry that referenced it.

Deleted messages¶

When a reviewer permanently removes a quarantined message, the message and all associated data are deleted from the database and can’t be recovered, including:

Message content and properties: The text of the message and any associated post properties.
File metadata: Information about files attached to the message (e.g., file names, IDs, and links to storage).
File metadata from edit history: Information about files attached to earlier versions of the message.
Edit history: All previous versions of the message and their timestamps.
Uploaded files: The actual files stored in Mattermost’s file storage (local, S3, etc.).
Priority data: Any message priority or importance settings.
Acknowledgements: Records of users who acknowledged the message.
Reminders: Any reminders created for the message.

Best practice recommendations¶

Before rolling out Data Spillage Handling organization-wide, we recommend communicating that the feature protects both users and the organization from accidental data spillage. Start with a pilot team to validate reviewer notifications and workflows, integrate the process with existing data-handling or incident-response playbooks, and require reporter and reviewer comments to ensure every decision is transparent and auditable.