# Phishing Credential Exfiltration via EmailJS and React Frameworks

> Security analysis of a sophisticated React-based phishing kit that leverages the EmailJS service for stealthy exfiltration of user credentials.

- Published: 2026-03-13T08:18:34.000Z
- Severity: medium
- Category: Threat Intel
- Tags: Phishing, EmailJS, React, Credential Theft, SANS ISC
- Author: Runtime Rebel Intel
- Primary source: https://isc.sans.edu/diary/rss/32794
- Canonical: https://runtimerebel.com/blog/phishing-credential-exfiltration-via-emailjs-and-react-frameworks

## Key points

- Attackers are using React-based phishing pages and legitimate email services to steal user credentials while bypassing traditional network detection.
- Systems at risk include any organization whose users may encounter malicious URLs leading to these dynamically generated credential-harvesting sites.
- Defenders should monitor for unexpected traffic to EmailJS domains and implement robust multi-factor authentication to mitigate the impact of stolen credentials.

A recent investigation into a malicious [Phishing](/glossary#phishing) campaign reveals a significant shift in how attackers architect credential-harvesting pages. According to researchers at [SANS ISC](https://isc.sans.edu/diary/rss/32794), threat actors are now utilizing modern JavaScript frameworks like React and legitimate third-party communication platforms to exfiltrate stolen data. This approach represents a more sophisticated [TTP](/glossary#ttp) compared to traditional static HTML phishing pages, as it leverages dynamic rendering and whitelisted services to evade security controls.

## Technical Analysis of the Attack Chain

The attack begins with a standard email lure, though the technical execution of the landing page is what distinguishes this campaign. Instead of a simple form, the attacker-controlled site is built using React, a popular JavaScript library for building user interfaces. The use of React allows the phishing kit to be modular and more difficult to analyze through automated scanning tools that often struggle with heavily scripted dynamic content. This **React-based phishing kit analysis** demonstrates that the page components are rendered client-side, making the initial static response from the server appear benign to some basic web filters.

Once a victim enters their credentials into the fraudulent form, the page does not use a traditional [C2](/glossary#c2) server to collect the data. Instead, it integrates the `emailjs-com` library. EmailJS is a legitimate service that allows developers to send emails directly from client-side JavaScript without needing a dedicated backend server. By embedding the attacker's EmailJS API keys and service IDs directly in the React components, the phishing page can transmit stolen credentials via an encrypted HTTPS request to the official EmailJS API endpoints.

### Phishing credential theft via legitimate email services

The most concerning aspect of this technique is its ability to bypass network-level monitoring. Many organizations implement [SIEM](/glossary#siem) and [SOC](/glossary#soc) alerts for POST requests directed at unknown or low-reputation domains. However, because the data exfiltration occurs via a connection to a trusted domain like `api.emailjs.com`, it is far more likely to be overlooked by automated security systems. Using this method for **phishing credential theft via legitimate email services** allows attackers to maintain a low profile and ensures that their exfiltration path remains open even if the specific phishing landing page is taken down.

## Detection and Remediation Strategies

Defenders must adapt their detection logic to account for the abuse of legitimate SaaS platforms in the final stages of an attack. Traditional [IoC](/glossary#ioc) lists that focus solely on malicious domains are insufficient when the infrastructure being used for data transit is legitimate.

### How to detect EmailJS phishing exfiltration

To identify this activity, [SOC](/glossary#soc) teams should monitor for unusual spikes in outbound traffic to `api.emailjs.com` or `cdn.emailjs.com`, particularly from internal systems that have no business requirement to interact with such services. Integrating these logs into a [SIEM](/glossary#siem) for correlation with web proxy logs can help identify the initial [Phishing](/glossary#phishing) link that preceded the API call.

Furthermore, practitioners should consider the following [MITRE ATT&CK](/glossary#mitre-att-ck) focused mitigations:

*   **Enhanced Endpoint Visibility:** Deploy [EDR](/glossary#edr) solutions that can inspect browser process behavior and identify the loading of scripts related to email automation libraries on untrusted sites.
*   **Multi-Factor Authentication (MFA):** While not a detection method for the kit itself, MFA remains the most effective defense against the successful use of stolen credentials.
*   **Content Security Policy (CSP):** Organizations hosting their own web assets should implement strict CSP headers to prevent unauthorized scripts from executing, although this is more effective for preventing [XSS](/glossary#xss) than for stopping users from visiting external phishing sites.

**Related:** [Phishing Campaign Leverages Fake Google PWA to Steal Credentials, MFA](/blog/phishing-campaign-leverages-fake-google-pwa-to-steal-credentials-mfa), [Phishing Alert: Impersonation of US City/County Officials Targets Permit Applicants](/blog/phishing-alert-impersonation-of-us-city-county-officials-targets-permit-applicants)

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