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Security audit

sendmux-token-efficient-usage

Security checks for vulnerabilities and agentic risk

Overview

This is a Sendmux usage guide that discloses account and credential needs and gives scoped, efficiency-focused instructions for email, mailbox, and management workflows.

Install this only if you intend to let your agent work with Sendmux. Use scoped Sendmux credentials where possible, review any requested send, delete, or management action before it runs, and avoid granting root-level management keys unless the task truly requires them.

A.I.G

Vulnerability Patterns
  • Skill Instruction HijackingAlters the agent's session goals or safety constraints when the skill loads
  • Agent Memory PoisoningWrites attacker-controlled rules into memory that affect later sessions
  • Remote Payload Retrieval and ExecutionFetches external code whose behavior can change after review
  • Embedded Malicious CodeShips malicious scripts inside the skill and executes them locally
  • Unauthorized Access and Privilege EscalationObtains permissions beyond the task's legitimate needs

SkillSpector

Vulnerability Patterns
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
  • Excessive AgencyUnrestricted Tool Access, Autonomous Decision Making, Scope Creep
  • Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
  • Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
  • Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
Findings (7)

Autonomous Decision Making

Medium
Category
Excessive Agency
Confidence
80% confidence
Finding

Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.

Content

Scanner excerpt · SKILL.md (reported line 20)May include surrounding context.

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## ClawHub account note

This ClawHub skill connects OpenClaw agents to Sendmux. Some workflows require a Sendmux account and an appropriate Sendmux API key or agent token. Sendmux account usage is external to ClawHub; do not ask users to paste secrets into chat.

Use this skill to choose the lowest-cost Sendmux route that still answers the task correctly.

Autonomous Decision Making

Medium
Category
Excessive Agency
Confidence
80% confidence
Finding

Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.

Content

Scanner excerpt · SKILL.md (reported line 26)May include surrounding context.

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## Boundaries

- Do not ask the user to paste an API key.
- For API-key authentication, use `smx_mbx_*` keys for normal Mailbox calls.
- For a self-registered agent, reuse one durable CLI profile. Mailbox reads become available after provisioning, before owner approval; Sending stays blocked until owner approval.
- For API-key authentication, use `smx_root_*` for Management calls.

Whitespace Padding

Medium
Category
Prompt Injection
Confidence
70% confidence
Finding

Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Content

Scanner excerpt · SKILL.md (reported line 58)May include surrounding context.

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## Cheapest-call map

| Task                            | Cheapest correct default                                                                                                               |
| ------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |
| Send one outbound email         | `sending_send_email`, CLI `sending:send`, SDK `sendingSendEmail`; include `Idempotency-Key`.                                           |
| Send multiple outbound emails   | `sending_send_email_batch`, CLI `sending:send:batch`, SDK `sendingSendEmailBatch`; do not loop single sends.                           |

Whitespace Padding

Medium
Category
Prompt Injection
Confidence
70% confidence
Finding

Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Content

Scanner excerpt · SKILL.md (reported line 62)May include surrounding context.

md
| ------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |
| Send one outbound email         | `sending_send_email`, CLI `sending:send`, SDK `sendingSendEmail`; include `Idempotency-Key`.                                           |
| Send multiple outbound emails   | `sending_send_email_batch`, CLI `sending:send:batch`, SDK `sendingSendEmailBatch`; do not loop single sends.                           |
| Send or read attachments        | Use the attachment route reference below.                                                                                              |
| Count matching mailbox messages | `mailbox_count_messages`, CLI `mailbox:count-messages`, SDK `mailboxCountMessages`.                                                    |
| Search mailbox text             | `mailbox_search_message_snippets`, CLI `mailbox:search-message-snippets`, SDK `mailboxSearchMessageSnippets`; then fetch selected IDs. |
| Read several known messages     | `mailbox_batch_get_messages`, CLI `mailbox:batch-get-messages`, SDK `mailboxBatchGetMessages`.                                         |

Whitespace Padding

Medium
Category
Prompt Injection
Confidence
70% confidence
Finding

Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Content

Scanner excerpt · SKILL.md (reported line 66)May include surrounding context.

md
| Count matching mailbox messages | `mailbox_count_messages`, CLI `mailbox:count-messages`, SDK `mailboxCountMessages`.                                                    |
| Search mailbox text             | `mailbox_search_message_snippets`, CLI `mailbox:search-message-snippets`, SDK `mailboxSearchMessageSnippets`; then fetch selected IDs. |
| Read several known messages     | `mailbox_batch_get_messages`, CLI `mailbox:batch-get-messages`, SDK `mailboxBatchGetMessages`.                                         |
| Update/delete several messages  | Batch update/delete after explicit confirmation.                                                                                       |
| Resume broad mailbox sync       | `mailbox_get_changes`, CLI `mailbox:get-changes`, SDK `mailboxGetChanges`.                                                             |
| Resume filtered mailbox sync    | CLI/SDK `mailbox:query-message-changes` / `mailboxQueryMessageChanges`; MCP does not curate it yet.                                    |
| Watch live mailbox events       | CLI/SDK `mailbox:stream-events` / `mailboxStreamEvents`; MCP does not curate it yet.                                                   |

Whitespace Padding

Medium
Category
Prompt Injection
Confidence
70% confidence
Finding

Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Content

Scanner excerpt · SKILL.md (reported line 72)May include surrounding context.

md
| Count matching mailbox messages | `mailbox_count_messages`, CLI `mailbox:count-messages`, SDK `mailboxCountMessages`.                                                    |
| Search mailbox text             | `mailbox_search_message_snippets`, CLI `mailbox:search-message-snippets`, SDK `mailboxSearchMessageSnippets`; then fetch selected IDs. |
| Read several known messages     | `mailbox_batch_get_messages`, CLI `mailbox:batch-get-messages`, SDK `mailboxBatchGetMessages`.                                         |
| Update/delete several messages  | Batch update/delete after explicit confirmation.                                                                                       |
| Resume broad mailbox sync       | `mailbox_get_changes`, CLI `mailbox:get-changes`, SDK `mailboxGetChanges`.                                                             |
| Resume filtered mailbox sync    | CLI/SDK `mailbox:query-message-changes` / `mailboxQueryMessageChanges`; MCP does not curate it yet.                                    |
| Watch live mailbox events       | CLI/SDK `mailbox:stream-events` / `mailboxStreamEvents`; MCP does not curate it yet.                                                   |

Whitespace Padding

Medium
Category
Prompt Injection
Confidence
70% confidence
Finding

Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Content

Scanner excerpt · SKILL.md (reported line 70)May include surrounding context.

md
| Resume broad mailbox sync       | `mailbox_get_changes`, CLI `mailbox:get-changes`, SDK `mailboxGetChanges`.                                                             |
| Resume filtered mailbox sync    | CLI/SDK `mailbox:query-message-changes` / `mailboxQueryMessageChanges`; MCP does not curate it yet.                                    |
| Watch live mailbox events       | CLI/SDK `mailbox:stream-events` / `mailboxStreamEvents`; MCP does not curate it yet.                                                   |
| Scan threads                    | List threads, then fetch one thread or its messages.                                                                                   |
| Manage domains/mailboxes/keys   | Management MCP for curated create/list/get/update/suspend/resume/key tools; CLI/SDK for uncovered lifecycle work.                      |
| Manage sending accounts         | CLI/SDK; MCP does not curate provider tools yet.                                                                                       |
| Manage webhooks                 | MCP for list/create/test; CLI/SDK for get/update/delete/rotate/delivery payloads.                                                      |

Static analysis

No suspicious patterns detected.