RFC 6455, "The WebSocket Protocol", December 2011

Note: This RFC has been updated by RFC 7936, RFC 8307, RFC 8441

Errata ID: 6997
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Daniel Egger
Date Reported: 2022-06-17

Section 4.3, 9.1 says:

      extension-param = token [ "=" (token | quoted-string) ]
           ; When using the quoted-string syntax variant, the value
           ; after quoted-string unescaping MUST conform to the
           ; 'token' ABNF.

It should say:

      extension-param = token [ "=" (token | quoted-string) ]

Notes:

The text reads as if any quoted-string which was supplied as a value has to follow the same rules as a token. That precludes the use of any token separators inside a quoted-string which is the whole reason why quoted-string exists as explained in RFC 2616:

Many HTTP/1.1 header field values consist of words separated by LWS
or special characters. These special characters MUST be in a quoted
string to be used within a parameter value (as defined in section
3.6).

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