Secret leaks often occur when a sensitive piece of authentication data is stored with the source code of an application. Considering the source
code is intended to be deployed across multiple assets, including source code repositories or application hosting servers, the secrets might get
exposed to an unintended audience.
Why is this an issue?
In most cases, trust boundaries are violated when a secret is exposed in a source code repository or an uncontrolled deployment environment.
Unintended people who don’t need to know the secret might get access to it. They might then be able to use it to gain unwanted access to associated
services or resources.
The trust issue can be more or less severe depending on the people’s role and entitlement.
What is the potential impact?
Mailgun API keys provide complete control over the Mailgun account and allow sending bulk emails.
Below are some real-world scenarios that illustrate some impacts of an attacker exploiting the secret.
Compromise of sensitive personal data
This kind of service is often used to exchange information that could include personal information, chat logs, and other private data that users
have shared on the platform. This is called
Personally Identifiable Information.
The leaked app key could provide a gateway for unauthorized individuals to access and misuse this data, compromising the privacy and safety of the
In many industries and locations, there are legal and compliance requirements to protect sensitive data. If this kind of sensitive personal data
gets leaked, companies face legal consequences, penalties, or violations of privacy laws.
Phishing and spam
An attacker can use this secret to spam users or lure them into links to a malicious domain controlled by the attacker.
Spam can cause users to be exposed to the following:
- Unsolicited, inappropriate content, such as pornographic material
- Fraudulent attempts to trick users into sending information or money
- Abusive or hateful statements
- False advertising or fraudulent claims
Once a user has been phished on a legitimate-seeming third-party website, an attacker can collect the user’s credentials, bypass multi-factor
authentication (MFA), and take over the user’s account on the trusted website.
Due to this vulnerability, malware can be stored and spread, both to users of the service and to other potential targets.
A malware depends on
the attacker’s intentions, as the following examples show:
- Cryptojacking malware, whose goal is to "mine" cryptocurrencies on the affected computers or servers.
- Spyware that spies out sensitive information from victims.
In the worst case, malware can cause the target systems to be completely compromised and allow attackers to infiltrate the systems.
Unauthorized access to mailing service API keys can also result in resource abuse. Attackers can exploit the API keys to send a large volume of
spam emails or perform other resource-intensive operations, causing a significant strain on the mailing service provider’s infrastructure.
The service provider, being vigilant about such activities, may flag your account and take action against it. This could lead to the suspension or
termination of the compromised account, thus causing significant inconvenience and potential loss of communication with your customers or
How to fix it
Revoke the secret
Revoke any leaked secrets and remove them from the application source code.
Before revoking the secret, ensure that no other applications or processes are using it. Other usages of the secret will also be impacted when the
secret is revoked.
Use a secret vault
A secret vault should be used to generate and store the new secret. This will ensure the secret’s security and prevent any further unexpected
Depending on the development platform and the leaked secret type, multiple solutions are currently available.
Noncompliant code example