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Portal Walkthrough: Control 1.26 - Agent File Upload and File Analysis Restrictions

Last Updated: October 2026

Control 1.5 dependency checked 2026-10-16 (documentation only): Defender for Cloud Apps file policies retire January 6, 2027. Verify a supported connected-app repository, not assumed Dataverse/Power Platform file-policy coverage, and plan migration to Purview DLP or auto-labeling. This does not establish synchronous scanning of arbitrary direct agent uploads. No tenant/UI test was performed. Portals: Microsoft Copilot Studio, Power Platform Admin Center (PPAC), Microsoft Purview, Microsoft Defender XDR (Zone 3) Estimated Time: 20–40 minutes per agent (Zone 3 includes DLP and content-scanning verification)

Prerequisites

  • AI Administrator (canonical role per docs/reference/role-catalog.md) — primary owner for the per-agent File Upload toggle and allowed-file-type list
  • Power Platform Admin — required for environment feature flags, Dataverse environment capacity and security role review, and DLP scope
  • Purview Compliance Admin — required for DLP and sensitivity-label policy verification (Zone 2+)
  • Copilot Studio Agent Author (Environment Maker + agent ownership) — required to open agent Settings
  • Documented governance-zone classification for each target agent (Zone 1 / Zone 2 / Zone 3)
  • Approved file-upload enablement request with documented business justification (Zone 2+); formal risk assessment (Zone 3)
  • Companion: Control 1.25 (MIME Type Restrictions) implemented at the environment level — this control is per-agent and depends on environment-level allowlists for defense-in-depth

Scope note: This walkthrough governs the per-agent File Upload toggle in Copilot Studio. Environment-wide file-type and MIME allowlists are governed by Control 1.25. Apply both for layered protection.

Step-by-Step Configuration

Step 1: Confirm Agent Zone Classification and Approval State

  1. Open your agent inventory and confirm the agent's governance zone (1 / 2 / 3)
  2. For Zone 2 or Zone 3 agents, confirm an approved file-upload enablement request exists in your governance system of record (ServiceNow, SharePoint List, Dataverse, etc.)
  3. For Zone 3 agents, confirm a documented risk assessment is on file and approved by the AI Governance Lead or designate

Important: Do not toggle File Upload on for a Zone 2 or Zone 3 agent without the documented approval. Toggle changes are recorded in the Power Platform admin activity log and may surface during supervisory review.

Step 2: Open the Per-Agent File Upload Settings (Copilot Studio)

  1. Open Copilot Studio
  2. Select the target environment from the environment switcher (top-right)
  3. Open the target agent
  4. Click the agent name → Settings → Generative AI
  5. Navigate to the File processing capabilities section

Portal path (June 2026): Copilot Studio → [Environment] → [Agent] → Settings → Generative AI → File processing capabilities → File uploads. Older guidance referencing a "Security → File Upload" or "Knowledge" sub-tab is stale.

Step 3: Set the File Upload Toggle Per Zone

Zone Recommended Default Conditions to Enable
Zone 1 (Personal) On acceptable for personal-productivity use None beyond Microsoft defaults; periodic review
Zone 2 (Team) Off until approved Documented approval and DLP coverage in the agent's environment
Zone 3 (Enterprise) Off (default deny) Formal risk assessment, AI Governance Lead approval, DLP enforce mode, and Defender content scanning
  1. Toggle File Upload to the state determined by Step 1's approval check
  2. Click Save
  3. Republish the agent: Copilot Studio caches agent runtime configuration; the new toggle state may not be enforced for clients until the agent is republished

Caveats (verify before relying on the toggle as a governance control): - CMK environments: If the agent resides in a Customer Managed Key (CMK)-enabled environment, the toggle can be set to On but the agent will not process uploaded files. Document this as a compensating control gap. See Troubleshooting for the diagnostic symptom. - SharePoint channel: If the agent is published to a SharePoint channel, users cannot upload files regardless of the toggle state (per Microsoft Learn). Verify the channel matrix before treating the per-agent toggle as an authoritative governance control for SharePoint-published agents.

Step 4: Configure Allowed File Types (Per-Agent Allowlist)

Required for every Zone 2 and Zone 3 agent with File Upload = On. PPAC controls (Control 1.25) establish the maximum permitted file types for the environment; per-agent allowlists apply additional least-privilege restrictions.

  1. In the File processing capabilities section, locate Allowed file types (visible only when File uploads is On)
  2. Reduce the allowlist to the minimum set required by the agent's documented purpose
  3. Example: a contract-summary agent → .pdf only
  4. Example: a financial-analysis agent → .xlsx, .csv only
  5. Do not inherit the full environment allowlist by default
  6. Click Save and republish

Note: The supported file types for user runtime uploads (DOCX, CSV, PDF, TXT, JPG, PNG, WebP, non-animated GIF) are narrower than maker-uploaded knowledge source types (which include XML, HTML, JSON, YAML, and additional formats). Build Zone 3 allowlists against the current MS Learn supported types list for runtime uploads and the knowledge source types list for maker uploads.

Step 5: Verify File Size and Per-Conversation Limits

  1. Review and document the Microsoft-defined limits applicable to your agent (per Microsoft Learn):

    Source Limit
    Maker-uploaded knowledge files Up to 512 MB per file
    Knowledge files per agent (Dataverse / local upload) 500 files (see Copilot Studio quotas and limits)
    User-uploaded file at runtime (individual file size) 15 MB (see Allow file input from users)
    User-uploaded text file at runtime (character limit, without code interpreter) 30,000 characters per file

  2. For Zone 3, document any organizational reductions to these defaults (e.g., enforced via Defender for Cloud Apps file size policies) in the risk assessment

Note: Microsoft does not currently expose a per-agent setting to lower these defaults below platform values. Reductions must be enforced via complementary controls (Defender file policies, Purview DLP rules, network egress policies).

Multi-channel note: The 500-file limit applies to the Copilot Studio web app (Dataverse-stored knowledge). Multi-channel Zone 2/3 tenants should verify whether the Teams app surface exposes different file quota limits and document the applicable limits per channel in the risk assessment.

Step 6: Verify Sensitivity Label Display (Preview Feature)

Preview: Sensitivity label display in Copilot Studio agent responses is a preview feature per Microsoft Learn. Verify current GA status at View sensitivity labels in agent responses before treating this as a Regulated-zone baseline control.

  1. In Copilot Studio, navigate to the agent's Knowledge section
  2. If File Upload is On, upload two test files with different sensitivity labels applied at source (e.g., one Confidential and one Highly Confidential)
  3. Send a test query that causes the agent to cite both files in its response
  4. Confirm the response displays a shield icon showing the Highly Confidential label (the highest label among cited content in that response)
  5. Capture screenshot evidence of the response-level label shield and store under maintainers-local/tenant-evidence/1.26/ (gitignored)

Caveat: The documented behavior is per-response shield display of the highest label among content cited in that response — not an agent-level inherited property. If the shield does not appear, verify the source file's label and supported source/response behavior; do not assume Dataverse is a Purview auto-labeling policy location. See the Troubleshooting playbook.

Step 7: Verify DLP Policy Coverage (Zone 2+)

  1. Open Power Platform Admin Center and review the data policies that apply to the agent's environment. These are Power Platform connector policies, not a Power Platform location in Purview DLP.
  2. Review Business, Non-business, and Blocked classifications for the agent's knowledge sources, tools, and channels. For maker-uploaded local knowledge files, review Knowledge source with documents in Copilot Studio; SharePoint/OneDrive knowledge sources use a separate connector. See Configure data policies for agents.
  3. Test allowed and blocked resources in the scoped environment and retain the resulting enforcement evidence. Connector classification does not establish SIT inspection of arbitrary file contents or end-user uploads.
  4. Separately review Microsoft Purview DLP for each supported workload that stores or processes the test content. For Zone 3, retain the requirement for FSI-relevant Sensitive Information Types (US SSN, US Bank Account Number, Credit Card Number, ITIN, MNPI patterns), Block action, and override prohibited; verify the actual workload supports the required classifier/action and that the policy is enabled rather than in simulation. If an upload path lacks supported content inspection, record the coverage gap instead of treating a connector policy as evidence that this requirement is met.

Step 8: Configure Defender for Cloud Apps Content Scanning (Zone 3)

Required for Zone 3. Validate true-content-type inspection separately from declared extension/MIME settings. The connected-app pattern in Control 1.25 Step 7 applies only to supported repositories, not assumed Dataverse coverage or interception of direct agent uploads. Record an unsupported inspection path as a coverage gap with an approved compensating control; do not mark it protected based on an unrelated file policy.

  1. Open Microsoft Defender XDR portal → Cloud apps → Policies → Policy management → File policy
  2. Select a supported connected app that actually stores the files being tested. Do not assume Dataverse / Power Platform is a Defender for Cloud Apps file-policy location.
  3. Add filter: MIME type (true type) does not equal the approved per-agent allowlist
  4. Governance actions: Quarantine + Notify file owner + Notify SOC distribution list
  5. Create a High severity alert; forward to Microsoft Sentinel
  6. Save and confirm the policy is Enabled

Step 9: Review Dataverse Environment Storage Configuration

  1. Open Power Platform Admin Center → Environments → [Environment]
  2. Navigate to Resources → Capacity to review Dataverse storage consumption for the environment hosting the agent's knowledge files
  3. Navigate to Settings → Users + permissions → Security roles and verify:
  4. Access to the Dataverse tables storing knowledge files is restricted to authorized service principals and admin roles
  5. A Purview retention policy is applied (Zone 2+) that meets the agent's record-retention obligations under FINRA 4511 / SEC 17a-4(f)
  6. Dataverse auditing is enabled for the environment (Zone 2+)
  7. Capture the configuration as evidence (see PowerShell Setup for SHA-256 evidence emission)

Step 10: Update the Per-Agent Inventory

  1. Update the file-upload inventory with:
  2. Agent name and environment
  3. Zone classification
  4. Toggle state and allowed-file-type list
  5. Approval reference (ticket / record ID)
  6. Last review date and reviewer
  7. Schedule the next review at the zone-appropriate cadence (Zone 1 quarterly / Zone 2 monthly / Zone 3 weekly)

Configuration by Governance Level

Setting Baseline (Zone 1) Recommended (Zone 2) Regulated (Zone 3)
File Upload toggle default Allowed Disabled until approved Default deny
Per-agent allowed file types Microsoft defaults Reduced to documented purpose Minimum set; documented in risk assessment
Approval required No Documented approval Formal risk assessment + AI Governance Lead approval
Sensitivity label inheritance Recommended Required Required with audit trail
DLP policy coverage Not required Required (Enforce mode) Required + content scanning
Defender for Cloud Apps content scanning Not required Optional Required (true-MIME inspection)
Dataverse environment retention policy Recommended Required Required + auditing enabled
Sentinel monitoring Optional Optional Required
Inventory tracking Recommended Required Required
Review frequency Quarterly Monthly Weekly
Exception process Informal Documented Documented with approval

Validation

After completing these steps, verify:

  • Per-agent File Upload toggle state matches the agent's zone and approval status
  • Per-agent Allowed file types list is reduced to the minimum required by the agent's documented purpose (Zone 2+)
  • Sensitivity-label response shield test passes (agent response displays the highest sensitivity label of cited content — preview feature; see Step 6)
  • DLP policy in Enforce mode covers the agent's environment (Zone 2+)
  • Defender for Cloud Apps file policy with true-MIME inspection is Enabled (Zone 3)
  • Dataverse environment security roles, retention policy, and auditing are configured (Zone 2+)
  • Per-agent inventory updated with toggle state, approval reference, and next review date
  • Screenshot evidence captured under maintainers-local/tenant-evidence/1.26/ (gitignored — never push to the repository)

Back to Control 1.26 | PowerShell Setup | Verification & Testing | Troubleshooting

Updated: June 2026 | Version: v1.6.2 | UI Verification Status: Current