Summary
GYM One contains a stored cross-site scripting vulnerability in the administrator user list because profile fields are rendered without HTML output encoding. An attacker who can save a crafted first name, last name, or email value may cause script to execute in an administrator's browser when the user-management page is viewed, potentially enabling actions with that administrator's privileges.
GYM One contains a stored cross-site scripting vulnerability in the administrator user list because profile fields are rendered without HTML output encoding. An attacker who can save a crafted first name, last name, or email value may cause script to execute in an administrator's browser when the user-management page is viewed, potentially enabling actions with that administrator's privileges.
Affected context
The issue occurs in GYM One deployments where an attacker can create or modify user profile fields and an administrator later visits the user-management interface. The affected values are rendered in /admin/users/ without context-appropriate HTML encoding, allowing stored content to be interpreted as browser script rather than displayed strictly as data.
The issue occurs in GYM One deployments where an attacker can create or modify user profile fields and an administrator later visits the user-management interface. The affected values are rendered in /admin/users/ without context-appropriate HTML encoding, allowing stored content to be interpreted as browser script rather than displayed strictly as data.
Exploit preconditions
- Attack surface: The administrator user-list page in the web application
- Required access: Permission to create or modify a record containing the affected profile fields, or another trusted workflow that stores attacker-controlled values
- Trigger point: An administrator viewing
/admin/users/ - Why exploitation is possible: Stored input is inserted into an HTML response without output encoding, allowing browser-interpreted script content to persist until the record is removed or corrected
- Attack surface: The administrator user-list page in the web application
- Required access: Permission to create or modify a record containing the affected profile fields, or another trusted workflow that stores attacker-controlled values
- Trigger point: An administrator viewing
/admin/users/ - Why exploitation is possible: Stored input is inserted into an HTML response without output encoding, allowing browser-interpreted script content to persist until the record is removed or corrected
Why this happens
The underlying bug is a failure to apply context-appropriate output encoding when rendering stored user-controlled values in an HTML page. Because first name, last name, and email fields are treated as trusted markup rather than encoded data, specially crafted content can be interpreted as script by an administrator's browser. This behavior maps to CWE-79: Improper Neutralization of Input During Web Page Generation, commonly called cross-site scripting.
The underlying bug is a failure to apply context-appropriate output encoding when rendering stored user-controlled values in an HTML page. Because first name, last name, and email fields are treated as trusted markup rather than encoded data, specially crafted content can be interpreted as script by an administrator's browser. This behavior maps to CWE-79: Improper Neutralization of Input During Web Page Generation, commonly called cross-site scripting.
Potential impact
- An attacker may access data available to the administrator's browser session
- Malicious script could perform actions available to the administrator
- Administrative settings or user records could be changed
- The application may experience unauthorized account or data manipulation
- Persistent content could affect multiple administrators who view the affected record
- An attacker may access data available to the administrator's browser session
- Malicious script could perform actions available to the administrator
- Administrative settings or user records could be changed
- The application may experience unauthorized account or data manipulation
- Persistent content could affect multiple administrators who view the affected record
General mitigation guidance
Mitigation generally focuses on treating all profile fields as untrusted at the point of output.
Common defensive patterns include:
- Apply context-aware HTML output encoding to every user-controlled value rendered in the administrator interface
- Prefer framework templating systems that escape output by default
- Validate and constrain field formats where business requirements permit, while not relying on validation as a substitute for encoding
- Avoid rendering user-controlled values as raw HTML or executable browser content
- Use restrictive Content Security Policy controls as defense in depth
- Limit administrative privileges and session scope so a successful browser-side injection has less reach
- Provide workflows for identifying, correcting, and removing previously stored malicious values
Mitigation generally focuses on treating all profile fields as untrusted at the point of output.
Common defensive patterns include:
- Apply context-aware HTML output encoding to every user-controlled value rendered in the administrator interface
- Prefer framework templating systems that escape output by default
- Validate and constrain field formats where business requirements permit, while not relying on validation as a substitute for encoding
- Avoid rendering user-controlled values as raw HTML or executable browser content
- Use restrictive Content Security Policy controls as defense in depth
- Limit administrative privileges and session scope so a successful browser-side injection has less reach
- Provide workflows for identifying, correcting, and removing previously stored malicious values
How teams detect issues like this
Organizations can look for this class of issue through:
- Static analysis rules identifying unescaped database or request values in HTML templates and response construction
- Code review checks for raw-output helpers, disabled template escaping, and direct concatenation into HTML
- Dynamic testing that stores harmless markup markers in profile fields and verifies they are encoded when displayed
- Regression tests covering every administrator-facing view that renders user-controlled data
- Content Security Policy reporting and web-application monitoring for unexpected script activity
- Automated security review tools that flag data flows from persistence layers to browser-rendered output without encoding
Organizations can look for this class of issue through:
- Static analysis rules identifying unescaped database or request values in HTML templates and response construction
- Code review checks for raw-output helpers, disabled template escaping, and direct concatenation into HTML
- Dynamic testing that stores harmless markup markers in profile fields and verifies they are encoded when displayed
- Regression tests covering every administrator-facing view that renders user-controlled data
- Content Security Policy reporting and web-application monitoring for unexpected script activity
- Automated security review tools that flag data flows from persistence layers to browser-rendered output without encoding
