Is Slack MCP server safe?
What Slack MCP server does
The Slack MCP server lets an MCP client list channels, read channel history and threads, post messages and replies, add reactions, and read user profiles through the Slack API. The npm author field lists Anthropic, PBC, and npm marks the package as no longer supported. It needs a Slack bot token (SLACK_BOT_TOKEN) and team ID, with scopes such as channels:history, chat:write and users.profile:read. Before installing, create a dedicated Slack app with only the scopes you need, and set SLACK_CHANNEL_IDS to limit which channels the server lists.
- Node.js network egress
- npm prepare hook
- MCP tool surface detected
What to do: Nothing here argues against installing it. Grant the capabilities it lists only if you expect the tool to need them.
Slack MCP server is an MCP server analyzed by SkillTotal's deterministic static scanner. The scan found no malicious indicators. It can: install time execution, mcp tools detected and network egress — capabilities are what the code can do, not a verdict on intent. Risk score 0/100 (low).
@modelcontextprotocol/
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Automated static-analysis result. It can contain false positives and false negatives, and is not a claim about the intent of Slack MCP server's authors. Report a false positive.
Behavioral traits
How this component maps to the CSA agentic threat model. Descriptive — it never affects the risk score.
Findings (3)
package.json has a 'prepare' script (runs on git/local installs and before publishing).
"prepare": "npm run build",
Why it matters: Usually a build step, but confirm it doesn't fetch or run remote code.
Fix: Usually a legitimate build step; confirm it only builds and does not fetch or execute remote code.
The component makes outbound network requests.
const response = await fetch(`https://slack.com/api/conversations.list?${params}`, { headers: this.botHeaders });const response = await fetch(`https://slack.com/api/conversations.info?${params}`, { headers: this.botHeaders });const response = await fetch("https://slack.com/api/chat.postMessage", {const response = await fetch("https://slack.com/api/chat.postMessage", {const response = await fetch("https://slack.com/api/reactions.add", {const response = await fetch(`https://slack.com/api/conversations.history?${params}`, { headers: this.botHeaders });const response = await fetch(`https://slack.com/api/conversations.replies?${params}`, { headers: this.botHeaders });const response = await fetch(`https://slack.com/api/users.list?${params}`, {const response = await fetch(`https://slack.com/api/users.profile.get?${params}`, { headers: this.botHeaders });Why it matters: Usually legitimate, but confirm the destinations are expected and no sensitive data leaves.
Fix: Confirm the destination hosts are expected and that no sensitive data is sent off-host.
An MCP tool surface (manifest or tool definitions) was found.
const server = new Server({server.setRequestHandler(CallToolRequestSchema, async (request) => {server.setRequestHandler(ListToolsRequestSchema, async () => {const transport = new StdioServerTransport();
Why it matters: Just context — review which tools it offers and their permissions.
Fix: Review the declared MCP tools and their permissions.
How attackers abuse these capabilities
Interactive labs on the attack class behind the rules above. They show the technique, not anything found in Slack MCP server.
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Scan your own componentHow we determine this: deterministic static analysis (regex + AST), evidence-anchored, no code execution. Methodology →