fix: fall back to JSON when JSONP callback sanitizes to empty#7161
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andrewstellman wants to merge 1 commit intoexpressjs:masterfrom
Open
fix: fall back to JSON when JSONP callback sanitizes to empty#7161andrewstellman wants to merge 1 commit intoexpressjs:masterfrom
andrewstellman wants to merge 1 commit intoexpressjs:masterfrom
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Move callback charset sanitization before the JSONP branch check so
that a callback consisting entirely of disallowed characters (e.g.
"!!!") is reduced to an empty string before the length test. Previously
the response entered the JSONP path, set Content-Type to
text/javascript, then sanitized the callback to empty, producing
malformed JavaScript:
/**/ typeof === 'function' && ({"count":1});
Now the sanitized-empty callback falls through to the plain JSON path
and returns valid application/json.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
res.jsonp()sanitizes the callback parameter by stripping disallowed characters (/[^\[\]\w$.]/g), but the JSONP branch is entered before sanitization. A callback consisting entirely of disallowed characters (e.g.!!!) passes thecallback.length !== 0check, setsContent-Type: text/javascript, then sanitizes to an empty string, producing malformed JavaScript:This patch moves the sanitization step before the JSONP branch check so an all-invalid callback is reduced to empty first and falls through to the plain JSON path, returning valid
application/json.Changes
lib/response.js— Movecallback.replace(…)before thecallback.length !== 0guard.test/res.jsonp.js— Add regression test:?callback=!!!expectsapplication/jsonwith valid JSON body.Test plan
text/javascriptwith malformed JS)application/jsonwith{"count":1})res.jsonptests pass