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Handlebars versions prior to 4.7.7 are vulnerable to prototype pollution when compiling templates obtained from an untrusted source with the compat compilation option enabled (compat: true). A crafted template can manipulate JavaScript object prototype properties during template compilation. In affected application contexts, this condition can be leveraged toward remote code execution.
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compat compilation option where it is not strictly required. Restrict template-authoring and template-upload capabilities to trusted users until the dependency can be updated.Patch, then assume compromise.
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository provides a proof-of-concept exploit and a scanner for CVE-2021-23383, a prototype pollution vulnerability in Handlebars versions before 4.7.7. The main exploit script (handlebars_exploit.py) sends a specially crafted Handlebars template in a JSON payload to a user-specified URL, attempting to pollute the prototype on the server. If the server is vulnerable, the script reports success. The scanner script (handlebars_scanner.py) attempts to detect the Handlebars version used by a target web service and reports if it is vulnerable. The repository is structured with a README describing the vulnerability, an exploit script, and a scanner script. Both scripts are written in Python and require the user to provide the target URL. No hardcoded endpoints are present; all targets are user-supplied.
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4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Compiling untrusted templates with compat:true in nodejs-handlebars can result in remote code execution.
A remote-code-execution vulnerability when nodejs-handlebars compiles untrusted templates using the compat:true option.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.