AI agents use putBase64 to create or update resources in Tencent Cloud COS MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Tencent Cloud COS MCP Server environment.
This tool writes/creates data in Tencent Cloud COS by uploading base64-encoded content. While reversible (files can be deleted), it modifies cloud storage state. Severity is medium because misuse could fill storage quotas, overwrite important files, or store malicious content, but the impact is limited to the target bucket without affecting financial systems or enabling destructive operations beyond the write scope.
From the tool's definition Tool name 'putBase64' and description '上传base64编码内容到存储桶' (upload base64-encoded content to storage bucket) indicates this creates/writes data to cloud storage. The 'put' verb and explicit upload action confirm data modification.
Documented attack patterns abuse exactly the kind of access putBase64 gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Tencent Cloud COS MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for putBase64:
{
"version": "1",
"default": "deny",
"tools": {
"putBase64": {
"limits": [
{
"counter": "putbase64_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}putBase64 stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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上传base64编码内容到存储桶. It is categorised as a Write tool in the Tencent Cloud COS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Tencent Cloud COS MCP Server MCP server in PolicyLayer and add a rule for putBase64: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Tencent Cloud COS MCP Server. Nothing to install.
putBase64 is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the putBase64 rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for putBase64. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
putBase64 is provided by the Tencent Cloud COS MCP Server MCP server (tencent/cos-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 21 Tencent Cloud COS MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
21 Tencent Cloud COS MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.