Password logged in plaintext in "malformed dsn" error (DATA_SOURCE_PASS with a space) #1408

What did you do?

Ran the exporter with the connection split across DATA_SOURCE_URI, DATA_SOURCE_USER and DATA_SOURCE_PASS, using a password that contains a space (a dummy value here):

docker run --rm \
  -e DATA_SOURCE_URI='127.0.0.1:5999/demo?sslmode=disable' \
  -e DATA_SOURCE_USER=demo \
  -e DATA_SOURCE_PASS='dummy secret-PW' \
  quay.io/prometheuscommunity/postgres-exporter:v0.20.1

What did you expect to see?

The connection error logged with the password redacted, as it already is in the URL form of the DSN (postgresql://demo:PASSWORD_REMOVED@...).

What did you see instead? Under which circumstances?

The "malformed dsn" error also quotes the key/value form of the DSN, and that copy contains the plaintext password:

level=ERROR source=postgres_exporter.go:606 msg="error scraping dsn" err="Error opening connection to database (postgresql://demo:PASSWORD_REMOVED@127.0.0.1:5999/demo?sslmode=disable): malformed dsn \"dbname='demo' host='127.0.0.1' password='dummy secret-PW' port='5999' sslmode='disable' user='demo'\"" dsn="postgresql://demo:PASSWORD_REMOVED@127.0.0.1:5999/demo?sslmode=disable"

The redaction is applied to the URL, but the error string from the DSN parser is passed through verbatim. Anyone who ships container logs to a central log store (Loki, Elasticsearch and similar) gets the database password there.

There are two separate problems:

1. The password is not redacted in the wrapped "malformed dsn" error.
2. A password containing a space is not accepted when it comes from DATA_SOURCE_PASS, even though it is valid in PostgreSQL. This looks like the same underlying issue as Passwords with blanks are not working #393, which was closed in July 2026 without a fix. It is the trigger that makes the parser error, and with it the leak, appear.

The same parser error is the one quoted in #393 (malformed dsn "... password=..."), so the leak itself is already visible publicly in that issue.

Environment

• System information:

  Linux 5.15.167.4-microsoft-standard-WSL2 x86_64 (Docker)

• postgres_exporter version:

  postgres_exporter, version 0.20.1 (branch: HEAD, revision: 867fbca)

• postgres_exporter flags:

(none; image defaults)

• PostgreSQL version:

  Not relevant. The error occurs before any connection is attempted. Also seen against PostgreSQL 18.6.

• Logs:

time=2026-10-10T15:40:19.609Z level=ERROR source=postgres_exporter.go:606 msg="error scraping dsn" err="Error opening connection to database (postgresql://demo:PASSWORD_REMOVED@127.0.0.1:5999/demo?sslmode=disable): malformed dsn \"dbname='demo' host='127.0.0.1' password='dummy secret-PW' port='5999' sslmode='disable' user='demo'\"" dsn="postgresql://demo:PASSWORD_REMOVED@127.0.0.1:5999/demo?sslmode=disable"