Slack Security: 8 Key Risks and Best Practices for Admins & Employees
Understanding the Importance of Slack Security
Slack is a core platform for team communication, decision-making, and file sharing. Its speed and reach boost productivity but also create gaps that both attackers and careless actions can exploit.
Sensitive data regularly moves through channels, direct messages, and connected apps. Without strict oversight, that information may be exposed to unauthorized access, insider activity, or external threats. As Slack becomes more embedded in daily operations, its security becomes essential. Effective Slack security protects data, builds trust across teams, and keeps organizations aligned with regulatory standards.
Types of Sensitive Data Shared on Slack
Slack often contains high-value information that was never designed to be stored long-term. Identifying the categories of sensitive data commonly shared across workspaces is a critical step in understanding organizational risk.
- Credentials and API Keys: Authentication tokens, OAuth secrets, and login credentials are sometimes shared in direct messages or code snippets, exposing systems to unauthorized access if intercepted.
- Personally Identifiable Information (PII): Names, emails, phone numbers, addresses, and employee records can appear in conversations, support requests, or onboarding threads, increasing compliance risk.
- Internal Documents and Business Strategy: Slack is frequently used to circulate internal reports, strategic plans, product roadmaps, and performance reviews. This often happens without tracking who accessed or downloaded them.
- Legal and Financial Data: Contracts, invoices, tax records, and confidential legal discussions may be shared in channels, especially among finance or legal teams, making Slack a target for attackers seeking financial gain or regulatory advantage.
8 Key Security Risks in Slack
Slack's flexibility accelerates collaboration, but it also introduces a unique set of security risks. Each of the following issues can contribute to serious exposure if left unaddressed.
1. Excessive Data Retention
Slack retains message history and file data by default, often beyond the period required for operational or compliance purposes. Workspaces may store years of unfiltered conversations and attachments without custom data retention policies, increasing the risk of accidental exposure or regulatory violations. Many organizations fail to align Slack retention with internal data governance frameworks.
2. Phishing and Social Engineering Attacks
Attackers can exploit Slack’s internal trust dynamics by sending malicious links or impersonating team members through direct messages. Users are more likely to engage with phishing attempts inside a familiar interface, making Slack an effective vector for credential harvesting and payload delivery. The lack of native URL scanning or sender verification increases the likelihood of successful social engineering.
3. Third-Party App Vulnerabilities
Slack’s integration ecosystem includes thousands of third-party apps, many of which request broad OAuth scopes during installation. Without regular review, such practices can lead to SaaS sprawl, where redundant or high-risk tools accumulate across the workspace without centralized oversight. Improperly vetted apps may gain read or write access to messages, files, and user data. In one documented case, a Slack-connected GenAI tool gained unauthorized administrative access to a linked Salesforce instance, exposing sensitive data through an unapproved SaaS-to-SaaS path.
4. Guest User and External Collaborator Risks
Guest users often outlast their intended purpose. Without strict offboarding protocols and scheduled reviews, former contractors or third-party vendors may retain access to internal channels and documents. These accounts may not be subject to the same identity verification or monitoring as core users, creating blind spots in security coverage.
5. Admin Role Mismanagement
Slack admins and owners hold high privileges, including the ability to modify user roles, create groups, and change workspace settings. In many organizations, these roles are distributed too broadly, leading to elevated risk from accidental misconfiguration or malicious intent. The platform does not enforce granular delegation by default, so access creep can quickly escalate.
6. No End-to-End Encryption
While Slack encrypts data at rest and in transit, it does not support true end-to-end encryption. This limitation means data remains accessible to Slack’s systems and personnel, raising concerns for organizations handling classified or highly regulated content. Internal audit and policy controls exist, but they do not eliminate access at the platform level.
7. Publicly Shared Links
Users can generate public links for files and messages without realizing that the content becomes accessible to anyone with the URL. The Figma vulnerability in Slack previews is one example, where a file link generates a preview image visible to users who may not have direct access to the original design. These links can be indexed, forwarded, or leaked through intentional sharing or accidental disclosure. Admins often overlook these links in security reviews unless external file sharing is actively monitored.
8. Insider Threats and Shadow IT
Slack allows employees to install apps, create private channels, and share information without formal review. These actions often occur outside the scope of IT governance, forming a parallel workflow that introduces risk. Shadow IT emerges when users bypass official tools or processes, making it harder for security teams to monitor access and enforce controls. Insider threats—both intentional misuse and accidental exposure—can go undetected without behavior monitoring or SaaS integration visibility.
Slack’s Built-In Security Features
Slack includes a range of native controls that support secure communication, access management, and compliance readiness. These features are designed to help organizations protect sensitive data, monitor activity, and align with regulatory expectations. While these tools are effective, they must be configured and maintained with care to meet real-world security needs.
The table below outlines Slack’s key built-in security features and the value they provide across operational, compliance, and administrative domains:
Slack Security Best Practices for Admins
Admins play a central role in defining and maintaining the security posture of a Slack workspace. Effective administration goes beyond basic setup as it requires ongoing reviews, proper access governance, and alignment with broader compliance strategies. The following practices help reduce risk and maintain control in a dynamic Slack environment:
- Conduct Regular Security Audits
Review workspace settings, channel configurations, and user roles on a scheduled basis. Identify deviations from policy, unused apps, and accounts with elevated access that no longer require it. - Review Slack Audit Logs
Use Slack’s Audit Logs API to monitor events such as logins, permission changes, and app activity. Integrate logs with SIEM tools to detect anomalies and track behavior over time. - Align Slack Usage with Compliance Standards
Map Slack configurations and usage patterns to frameworks like SOC 2, HIPAA, or ISO 27001. This procedure includes enforcing encryption, documenting retention policies, and maintaining clear records of administrative actions. - Enforce Least Privilege Access
Assign roles based on operational necessity. Limit the number of admins and workspace owners and periodically review these assignments to prevent privilege creep. - Restrict App Install Permissions
Control who can install third-party apps to prevent unauthorized integrations. Require approval workflows for new apps and review existing integrations for unnecessary access scopes. - Configure Mandatory Two-Factor Authentication (2FA)
Require 2FA for all Slack users. If using an identity provider with SAML-based SSO, enforce 2FA at the provider level to protect initial authentication.
Dr. Tal Shapira
Cofounder & CTO at Reco
Tal is the Cofounder & CTO of Reco. Tal has a Ph.D. from Tel Aviv University with a focus on deep learning, computer networks, and cybersecurity and he is the former head of the cybersecurity R&D group within the Israeli Prime Minister's Office. Tal is a member of the AI Controls Security Working Group with CSA.
Expert Tip: Strengthen Slack Security from the Ground Up
In my experience working with SaaS security teams, most Slack-related risks don’t come from the obvious settings but from misalignment between Slack’s flexibility and an organization's structure. That’s why it's important to take a layered approach. Here’s what I recommend:
- Create an Internal Slack Security Policy: Before enforcing controls, define what “secure use” looks like. This approach avoids confusion later when permissions are locked down.
- Segment App Approval Workflows: Set different approval paths for low-risk vs. high-risk apps to avoid bottlenecks and still control third-party access.
- Automate Stale Account Checks: Use scheduled reports or automated scripts to flag inactive users and guest accounts that may no longer need access.
The Takeaway: Treat Slack like any other enterprise application, with clearly defined access boundaries, review cycles, and usage guidelines. It's the daily details that make the difference.
Slack Security Best Practices for Employees
When it comes to securing a Slack workspace, employees often play a very important role. Their daily actions directly influence the organization's exposure to risk. By following clear practices, users can help protect sensitive data and reduce the likelihood of accidental or malicious incidents.
- Avoid Sharing Sensitive Info in Public Channels
Keep credentials, personal data, internal documents, and financial details out of public channels. Use private, access-controlled spaces for anything that could impact privacy or compliance. - Be Cautious with Link and File Sharing
Before sharing a link or file, confirm that the recipient needs access and that no confidential information is included. Avoid generating public links unless specifically required and approved. - Report Suspicious Activity
Unusual messages, unexpected file shares, or strange app behavior should be flagged to the security team. Phishing attempts in Slack often mimic internal communication patterns, making quick reporting essential. - Use Strong, Unique Passwords
Avoid reusing passwords across services. Encourage the use of password managers and enforce length and complexity standards through organizational policy. - Complete Slack Security Awareness Training
Regular training helps employees understand how Slack fits into the broader security strategy. Sessions should cover best practices, known risks, and changes to internal Slack policies.
Slack Privacy Settings & Concerns
Slack provides several privacy controls that help limit data exposure, but these settings do not fully eliminate privacy risks. Admins and security teams must understand what can be configured and where the platform’s architecture introduces residual concerns.
Slack Privacy Settings
The table below outlines key privacy settings available in Slack and their impact on data exposure and control.
Slack Privacy Concerns
While Slack offers configurable privacy controls, the following platform-level concerns may still affect organizational privacy strategy.
Compliance and Regulatory Considerations
Slack supports a range of compliance requirements, but meeting regulatory standards depends on how the platform is configured and monitored. Admins must understand both Slack's capabilities and their responsibilities to maintain compliance in regulated environments.
Slack and GDPR
Slack offers features that support GDPR compliance, but it does not assume responsibility for full adherence. Under GDPR, Slack acts as a data processor, while the organization using Slack is the data controller. This distinction means workspace admins must ensure that personal data shared in Slack is collected, stored, and retained according to legal guidelines.
Slack provides tools such as data export capabilities, user access logs, and custom data retention settings. These help fulfill rights such as data access, rectification, and erasure. However, GDPR compliance also requires a clear internal process for identifying and managing personal data stored in messages, files, and integrations. Organizations must monitor how third-party apps process personal data and document each integration’s legal basis under GDPR.
HIPAA and Other Industry Standards
Slack offers a HIPAA-compliant version for Enterprise Grid customers, but only when used in combination with strict administrative, technical, and contractual controls. Enabling HIPAA compliance in Slack involves configuring the workspace to meet the minimum necessary use standard, enforcing audit controls, and restricting access based on user roles.
In addition to HIPAA, Slack supports compliance with standards such as ISO 27001, SOC 2, and FINRA. Meeting these requirements depends on how Slack is implemented across departments. Audit logs, Enterprise Key Management, and integration reviews play a key role in proving compliance readiness.
It is important to note that certification does not eliminate risk. Security and compliance teams must regularly review Slack’s settings, monitor access activity, and ensure that policies governing sensitive data use are aligned with industry standards.
How Reco Helps You Secure Slack
Reco enhances Slack security by providing visibility, identity governance, and continuous monitoring that goes beyond native platform capabilities. These features are designed to help security teams manage configuration drift, monitor sensitive access, and prevent data exposure across Slack environments.
- Configuration Monitoring and Slack Security Posture: Reco continuously scans Slack workspaces for misconfigurations and deviations from best practices. It alerts security teams when permissions, retention policies, or app settings introduce new risks, helping maintain a strong and compliant security posture over time.
- Identity and Access Governance: Reco tracks identity activity within Slack to ensure that access aligns with organizational policies. The process includes monitoring admin role assignments, guest user behavior, and permission changes that could signal potential risk.
- Slack Integrations Mapping: Reco maps all SaaS-to-SaaS integrations connected to Slack. It identifies risky third-party apps, excessive OAuth scopes, and unintended data flows. In one documented case, Reco detected an unapproved GenAI tool used by a Slack admin that had gained administrative access to a customer's Salesforce instance. This type of exposure would likely remain invisible without Reco’s integration-level visibility.
- User and Entity Behavior Analytics (UEBA): Reco applies behavior analytics to flag anomalies in user activity. Unusual login patterns, privilege escalations, or unexpected file access may indicate account compromise or insider threats. These insights help teams respond quickly before damage occurs.
Conclusion
Slack is no longer just a tool for quick updates or team banter. It now holds intellectual property, client conversations, legal documentation, and sensitive access links, all in one place. As the platform continues to absorb more business-critical workflows, the expectations for its security must rise to meet that complexity.
The future of Slack security will not depend on reactive fixes. It will be shaped by real-time context, integration-aware insights, and identity-driven visibility. Security leaders who recognize Slack as part of their broader SaaS architecture and SaaS security strategy will be better equipped to manage evolving risks. By mapping connections, monitoring behavior, and exposing risks that default tools often miss, Reco enables that shift. It gives security teams the awareness they need to anticipate threats before they escalate.
If you're seeking to enhance the security of your SaaS applications and gain comprehensive visibility into every app and identity, Reco offers an AI-based platform designed to integrate seamlessly via API within minutes. Book a demo today to see how Reco can help secure your SaaS ecosystem with ease.
Gal Nakash
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ABOUT THE AUTHOR
Gal is the Cofounder & CPO of Reco. Gal is a former Lieutenant Colonel in the Israeli Prime Minister's Office. He is a tech enthusiast, with a background of Security Researcher and Hacker. Gal has led teams in multiple cybersecurity areas with an expertise in the human element.
