Firefox Keeps Using the Old Proxy Account
An old proxy login can come from an active authentication session, a saved password, or integrated sign-in. Clearing website cookies addresses a different layer.
First confirm which proxy hostname and account the administrator or proxy log reports. An old username displayed by a website can be its own cookie-backed session, not the account used at the intermediary.
| Possible source | Next check |
|---|---|
| Active HTTP authentication session | Where the installed release offers active-login clearing, use that scope rather than only cached images. Close all Firefox processes before reopening to remove instance ambiguity. |
| Saved proxy credential | Look for a matching stored login and remove only the unwanted entry. |
| Integrated authentication | Check whether the OS identity and managed Authentication policy immediately supply the account again. |
Firefox's separate HTTP authentication cache is documented in Mozilla's issue record. Availability of a clearing UI depends on the installed version. Clearing website cookies addresses another layer.
Managed policy may intentionally permit proxy SPNEGO or NTLM. That is distinct from the endpoint address and ordinary website passwords. Change the mechanism supplying the unwanted identity instead of applying a long list of unrelated about:config switches.
For a task requiring another identity, use an arrangement supported by the proxy administrator. Repeatedly erasing every website's cookies cannot establish that account ownership.