Automatically updates the Cookie header in Burp Repeater requests using Set-Cookie values from responses. This Bambda CustomAction preserves all existing cookies and only updates or adds values when necessary — ensuring session continuity without overwriting unrelated cookies.

update_cookie_BambdaCA.java

// Revision 1 - originally developed by chatGPT for @irsdl
// Revision 2 - improved by ChatGPT to be more efficient using Burp APIs!
// Automatically updates the Cookie header in Burp Repeater requests using Set-Cookie values from responses. This Bambda CustomAction preserves all existing cookies and only updates or adds values when necessary — ensuring session continuity without overwriting unrelated cookies.

// 1. Grab the request & response
var request  = requestResponse.request();
var response = requestResponse.response();

// 2. Pull any Set-Cookie cookies from the response
var responseCookies = response.cookies();
if (responseCookies.isEmpty()) {
    logging.logToOutput("No Set-Cookie headers found; nothing to sync.");
    return;
}

// 3. Extract existing COOKIE parameters
var oldParams = request.parameters().stream()
    .filter(p -> p.type() == HttpParameterType.COOKIE)
    .collect(Collectors.toList());

// 4. Merge into a LinkedHashMap<String,String> (preserving insertion order)
var merged = new LinkedHashMap<String,String>();
for (var p : oldParams) {
    merged.put(p.name(), p.value());
}

boolean changed = false;
for (var c : responseCookies) {
    String oldVal = merged.get(c.name());
    if (!c.value().equals(oldVal)) {
        merged.put(c.name(), c.value());
        changed = true;
    }
}
if (!changed) {
    logging.logToOutput("✅ Cookies already up to date.");
    return;
}

// 5. Build new HttpParameter[] for the merged cookies
var newParamsList = new java.util.ArrayList<burp.api.montoya.http.message.params.HttpParameter>();
for (var entry : merged.entrySet()) {
    newParamsList.add(
      burp.api.montoya.http.message.params.HttpParameter
        .cookieParameter(entry.getKey(), entry.getValue())
    );
}
var newParamsArray = newParamsList.toArray(
    new burp.api.montoya.http.message.params.HttpParameter[0]
);

// 6. Remove old COOKIE params and add the new ones
var withoutOld = request.withRemovedParameters(
    oldParams.toArray(new burp.api.montoya.http.message.params.HttpParameter[0])
);
var newRequest = withoutOld.withAddedParameters(newParamsArray);

// 7. Push the updated request into the editor pane
httpEditor.requestPane().set(newRequest);

// 8. Log the new Cookie header
var headerValue = merged.entrySet().stream()
    .map(e -> e.getKey() + "=" + e.getValue())
    .collect(Collectors.joining("; "));
logging.logToOutput("✅ Synchronized cookies: " + headerValue);