A prototype pollution vulnerability in Parse Server allows authenticated attackers to bypass security controls and induce permanent schema corruption.

The flaw exists within the deep copy mechanism, which fails to safely handle prototype properties. An authenticated attacker can exploit this to inject unauthorized fields into class schemas, bypassing both the request keyword denylist and class-level permission settings.

The ability to manipulate class schemas can lead to significant data integrity issues and persistent service disruption. Because the resulting schema type conflicts cannot be resolved even with the master key, this vulnerability poses a risk of permanent, irreversible damage to the backend database architecture, justifying its High severity CVSS score of 7.5.

Immediate Action: Update Parse Server to version 9.6.0-alpha.20 or 8.6.44, where the vulnerable third-party deep copy library has been replaced with a secure, built-in mechanism.

Proactive Monitoring: Review application logs for unusual request patterns or attempts to modify restricted schema fields, particularly those involving unexpected object prototype attributes.

Compensating Controls: While no specific workarounds exist, ensure that access to backend management functions is strictly limited to authorized personnel to reduce the attack surface for authenticated users.

Public Exploit Available: Unknown

Given the potential for irreversible schema corruption, administrators should prioritize patching Parse Server immediately. The complexity of resolving conflicts caused by this prototype pollution makes prevention through timely updates the only effective strategy for maintaining backend integrity.