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fix: block prototype pollution in files.js (CWE-1321) #755

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fix: block prototype pollution in files.js (CWE-1321) #755

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14 changes: 12 additions & 2 deletions main/files.js
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Original file line number Diff line number Diff line change
Expand Up @@ -115,10 +115,20 @@ export function saveWorkspace(workspace) {
}

function validateBlocklyJson(json) {
// 1. Parse JSON safely
// 1. Parse JSON safely. Reject dangerous keys via a reviver so they are
// rejected as each one is parsed, before they can ever be attached to an
// object - closing the window between JSON.parse() and the post-parse
// dangerous-key check below.
function safeReviver(key, value) {
if (key === '__proto__' || key === 'constructor' || key === 'prototype') {
throw new Error(`Dangerous property found: ${key}`);
}
return value;
}

let data;
try {
data = typeof json === 'string' ? JSON.parse(json) : json;
data = typeof json === 'string' ? JSON.parse(json, safeReviver) : json;
} catch {
throw new Error('Invalid JSON format');
}
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