Parse Server has denylist `requestKeywordDenylist` keyword scan bypass through nested object placement

Impact

The requestKeywordDenylist security control can be bypassed by placing any nested object or array before a prohibited keyword in the request payload. This is caused by a logic bug that stops scanning sibling keys after encountering the first nested value. Any custom requestKeywordDenylist entries configured by the developer are equally by-passable using the same technique.

All Parse Server deployments are affected. The requestKeywordDenylist is enabled by default.

Patches

The fix replaces the recursive object scanner with an iterative stack-based traversal that processes all nested values without prematurely exiting the scan loop. This also eliminates a potential stack overflow on deeply nested payloads.

Workarounds

Use a Cloud Code beforeSave trigger to validate incoming data for prohibited keywords across all classes.

References

• GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-q342-9w2p-57fp
• Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.1-alpha.1
• Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.12