Docs: CF supports only harmless workloads.

Document that ClusterFuzz should only be used for harmless workloads,
until we have VM-isolated job types.

Change-Id: I58646d0936bb176667ff6b8d7b643c132ae18ace
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3562180
Reviewed-by: Jonathan Metzman <[email protected]>
Commit-Queue: Adrian Taylor <[email protected]>
Cr-Commit-Position: refs/heads/main@{#987319}
diff --git a/docs/security/clusterfuzz-for-sheriffs.md b/docs/security/clusterfuzz-for-sheriffs.md
index 7f1c81a..961ce23 100644
--- a/docs/security/clusterfuzz-for-sheriffs.md
+++ b/docs/security/clusterfuzz-for-sheriffs.md
@@ -16,6 +16,9 @@
 Please *do* specify the crbug number when uploading the test case. This will allow
 ClusterFuzz to keep the crbug updated with progress.
 
+Please *don't* upload test cases unless they're obviously harmless. Currently
+ClusterFuzz does not support untrusted workloads.
+
 ## Useful jobs
 
 You should chose the right job type depending on the format of file you want to