fix(security): fix 4 security issues in handlebars, google-protobuf

[aikido-autofix]

Which Linear task belongs to this PR?

🔗 Related Tasks

• https://linear.app/lifi-linear/issue/PAR-901/major-upgrade-for-google-protobuf
• https://linear.app/lifi-linear/issue/EXSC-1199/aikido-fix-4-security-issues-in-handlebars-google-protobuf-contracts

Why did I implement it this way?

Upgrade Handlebars and google-protobuf to fix critical RCE vulnerabilities via unsafe AST compilation and prototype pollution, XSS via unescaped script tags, and DoS via unbounded group recursion.

Checklist before requesting a review

• I have performed a self-review of my code
• This pull request is as small as possible and only tackles one problem
• I have added tests that cover the functionality / test the bug
• For new facets: I have checked all points from this list: https://www.notion.so/lifi/New-Facet-Contract-Checklist-157f0ff14ac78095a2b8f999d655622e
• I have updated any required documentation

Checklist for reviewer (DO NOT DEPLOY and contracts BEFORE CHECKING THIS!!!)

• I have checked that any arbitrary calls to external contracts are validated and or restricted
• I have checked that any privileged calls (i.e. storage modifications) are validated and or restricted
• I have ensured that any new contracts have had AT A MINIMUM 1 preliminary audit conducted on by <company/auditor>

Security Impact — CVE vulnerabilities fixed by this PR

✅ 4 CVEs resolved by this upgrade, including 2 critical 🚨 CVEs

This PR will resolve the following CVEs:

Issue	Severity	Description
AIKIDO-2026-970464	🚨 CRITICAL	[handlebars] A vulnerability in AST validation allows arbitrary JavaScript injection through unchecked values in compile() and precompile() functions when processing untrusted ASTs, enabling remote code execution on the server or in precompiled output environments.
AIKIDO-2026-258160	🚨 CRITICAL	[handlebars] A prototype pollution vulnerability allows attackers to access the Function constructor and execute arbitrary code through templates using allowProtoMethodsByDefault: true, by exploiting the constructor property before the deny list is applied. The vulnerability enables remote code execution on the server when templates can reach prototype objects through accessible functions in the render context.
AIKIDO-2026-869467	MEDIUM	[handlebars] A vulnerability in template precompilation fails to escape </script> sequences in generated JavaScript, allowing injected script tags to execute in the browser when precompiled output is embedded inline in HTML documents. This enables arbitrary code execution for applications that precompile untrusted templates.
AIKIDO-2026-834673	HIGH	[google-protobuf] Unbounded recursion in group field skipping causes stack exhaustion when deserializing malicious protobuf messages with deeply nested groups, leading to denial of service through process crash.

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