Proofpoint TAP Click Rewrite Breaks a Vendor Link: Decode Before You Allowlist the World

Proofpoint · Techclick CLI troubleshooting lab

Users say a vendor button is broken in email. The same URL works when pasted. TAP URL defense is on.

This is a live-ticket style lesson from Techclick Infosec. You will isolate the fault with CLI first, then prove the fix with one clean packet or log.

What you will be able to do

• Name the first CLI command to run on Proofpoint for this ticket

• Separate the layer that is actually broken from the layer people blame

• Apply one scoped fix instead of a global disable

• Prove the ticket closed with a session, log, or counter

Quick answer

Proofpoint rewrites URLs. Some vendors sign the original URL and reject the rewritten one. Decode and add a targeted rewrite exception.

Why this ticket shows up

The rewrite is working as designed and still breaking a signed URL. That is a compatibility exception, not a TAP outage.

Symptoms operators actually see

• Link from email 403s on the vendor

• Pasted original works

• URL starts with urldefense.proofpoint.com

• Only email path fails

CLI first — copy this block

Run these on the Proofpoint device or console named in the ticket. Do not skip the first show command — it tells you which later command matters.

# decode a rewritten URL (example pattern)
python3 - <<'PY'
import urllib.parse
u='https://urldefense.proofpoint.com/v2/url?u=https-3A__vendor.com_a&d=...'
print(urllib.parse.unquote(u))
PY
curl -I 'https://vendor.com/a'

How to read that output

If the vendor needs the original signed query string, rewriting breaks the signature. Exception that vendor domain in TAP.

Triage order

1. Copy the rewritten URL

2. Decode to the original

3. Prove the original works

4. Add a rewrite exception for that domain

5. Do not disable TAP URL defense

Classic traps

What you see	Real cause	Fix
Turn off TAP	One vendor signs URLs	Exception
Ask users to disable Safe Links in Outlook	This is TAP, not MDO	Wrong product
Allowlist the vendor on the firewall	The break is the rewrite	Wrong layer

Proof the ticket is closed

• Email button works

• URL defense still on for the rest

• Exception is one domain

Say this in an interview

A link that works pasted and fails from email is a rewriter until I decode it.

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