bcquality/microsoft/knowledge/privacy/no-pii-in-telemetry-message-string.md

bc-version	domain	keywords	technologies	countries	application-area
all	privacy	telemetry session-logmessage strsubstno pii customer-data employee-code filename	al	w1	all

Do not embed customer data in the telemetry message text

Description

Session.LogMessage's message argument is a plain Text. Unlike Error(), the platform does not inspect this string field-by-field — whatever is in the text is what telemetry receives. So a call that builds the message via StrSubstNo from customer-bearing fields ships those values to telemetry verbatim, regardless of the DataClassification argument on the same call. Flagged content includes customer names, email addresses, phone numbers, addresses, employee codes or IDs, attachment filenames, user-provided text that may carry PII, and dumps of Record content.

Best Practice

Keep the telemetry message a static, non-personal string ("Customer record processed", "Error processing uploaded file"). When structured context is genuinely needed, attach it through custom dimensions, where individual values can be reviewed and classified at the dimension level rather than baked into a free-text message.

If a pseudonymous identifier (record No., primary key value) genuinely belongs in the diagnostic, prefer attaching it through a custom dimension and set the call's DataClassification to match the data actually shipped — EndUserPseudonymousIdentifiers for pseudonymous IDs, CustomerContent for content-bearing telemetry. Changing the DataClassification alone does not make embedding a customer name into the message string acceptable; the data still ships in the message, and downstream consumers still see the literal string.

See sample: no-pii-in-telemetry-message-string.good.al.

Related

• session-logmessage-requires-dataclassification.md — every Session.LogMessage call must specify DataClassification; choose the value to match the actual data shipped, not the value that makes the entry retained the longest.
• featuretelemetry-customdimensions-no-pii.md — custom dimensions are the right surface for structured context, but they have their own PII rules.

Anti Pattern

Session.LogMessage('0000', StrSubstNo('Processed %1', Customer.Name), ...) — the customer name is in telemetry the moment the line runs. Detection signal: a StrSubstNo whose result is the second argument of Session.LogMessage. The same shape with FileName, EmployeeCode, or any record field is the same problem.

See sample: no-pii-in-telemetry-message-string.bad.al.