Details
### Summary
A ZIP file can contain two entries with the identical name. adm-zip keeps both in its internal entry list, but its name-lookup table only retains the last one written. `getEntry(name)` and `extractAllTo()` walk these two different internal structures, so they can each resolve a duplicate name to a *different* entry. An application that validates a named entry's contents via `getEntry()` before trusting an archive, then extracts the whole archive, can end up approving one file's content while a different file's bytes are what actually land on disk under that name.
### Details
- `zipFile.js:58-83` retains both entries in `entryList` but overwrites `entryTable[name]` with only the last one written.
- `adm-zip.js:83-95,658-663` uses `entryTable` for `getEntry()` lookups — returns the *last* duplicate.
- `adm-zip.js:769-914` iterates `entryList` for extraction — writes the *first* duplicate (sync, default overwrite policy).
### PoC
```js
const AdmZip = require('adm-zip');
const z = new AdmZip({ noSort: true });
z.addFile('a.txt', Buffer.from('FIRST'));
z.addFile('b.txt', Buffer.from('SECOND'));
const raw = Buffer.from(z.toBuffer());
// rename the a.txt entry to b.txt directly in the raw bytes
for (let at = raw.indexOf('a.txt'); at >= 0; at = raw.indexOf('a.txt', at + 5)) {
raw.write('b.txt', at);
}
const parsed = new AdmZip(raw, { noSort: true });
const validated = parsed.getEntry('b.txt').getData().toString();
parsed.extractAllTo(outDir, false);
// validated === "SECOND", but the file written to disk === "FIRST"
```
Reproduced on the pinned commit (`2b4d84087d45344643e0183756e19191d52815cc`)
### Impact
An application that checks a named entry's content before trusting an untrusted ZIP, then extracts it, can be made to approve different bytes than what actually gets written to disk — the classic check/use split that this kind of validate-then-extract pattern relies on.
