Summary
A critical server-side cross-site scripting vulnerability in Quasar Framework's SSR-only getHead() serializer allows attacker-influenced metadata to be inserted into generated HTML without context-appropriate encoding. If users can control values such as titles, product names, excerpts, or display names, they may inject executable markup into the server-rendered response before client hydration.
A critical server-side cross-site scripting vulnerability in Quasar Framework's SSR-only getHead() serializer allows attacker-influenced metadata to be inserted into generated HTML without context-appropriate encoding. If users can control values such as titles, product names, excerpts, or display names, they may inject executable markup into the server-rendered response before client hydration.
Affected context
The issue occurs in Quasar applications that:
- Use server-side rendering with the Meta plugin
- Generate page metadata through
useMeta() - Process attacker-influenced or insufficiently trusted metadata values
- Use the affected SSR serialization path to append metadata to raw HTML responses
The client-side apply() path is not affected because it uses DOM APIs that provide attribute encoding. Risk is concentrated in server-rendered responses where metadata is concatenated into HTML markup.
The issue occurs in Quasar applications that:
- Use server-side rendering with the Meta plugin
- Generate page metadata through
useMeta() - Process attacker-influenced or insufficiently trusted metadata values
- Use the affected SSR serialization path to append metadata to raw HTML responses
The client-side apply() path is not affected because it uses DOM APIs that provide attribute encoding. Risk is concentrated in server-rendered responses where metadata is concatenated into HTML markup.
Exploit preconditions
- Attack surface: Server-rendered HTML responses generated by Quasar's Meta plugin
- Required access: The ability to influence a value used in dynamic page metadata, directly or through application-managed content
- Trigger point: SSR serialization performed by
getHead()and insertion throughinjectServerMeta() - Why exploitation is possible: Metadata values are inserted into title, meta, link, or script markup without HTML text or quoted-attribute encoding, allowing an input value to escape its intended context
- Attack surface: Server-rendered HTML responses generated by Quasar's Meta plugin
- Required access: The ability to influence a value used in dynamic page metadata, directly or through application-managed content
- Trigger point: SSR serialization performed by
getHead()and insertion throughinjectServerMeta() - Why exploitation is possible: Metadata values are inserted into title, meta, link, or script markup without HTML text or quoted-attribute encoding, allowing an input value to escape its intended context
Why this happens
The underlying defect is context-insensitive output encoding during server-side HTML generation. The SSR serializer used a helper intended for attribute handling while interpolating untrusted values into multiple HTML contexts, including text nodes and quoted attributes, and then appended the resulting markup directly to the response.
This behavior maps primarily to CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') and is also related to CWE-116: Improper Encoding or Escaping of Output. The insecure pattern is raw HTML construction with encoding that does not match the destination context.
The underlying defect is context-insensitive output encoding during server-side HTML generation. The SSR serializer used a helper intended for attribute handling while interpolating untrusted values into multiple HTML contexts, including text nodes and quoted attributes, and then appended the resulting markup directly to the response.
This behavior maps primarily to CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') and is also related to CWE-116: Improper Encoding or Escaping of Output. The insecure pattern is raw HTML construction with encoding that does not match the destination context.
Potential impact
- An attacker may execute JavaScript in a victim's browser
- Session information or application data could be exposed
- Page content may be modified or impersonated
- User actions could be performed in the affected application context
- Search, sharing, or administrative workflows may be compromised
- An attacker may execute JavaScript in a victim's browser
- Session information or application data could be exposed
- Page content may be modified or impersonated
- User actions could be performed in the affected application context
- Search, sharing, or administrative workflows may be compromised
General mitigation guidance
Mitigation centers on using context-aware output encoding for every server-rendered HTML context and avoiding raw string concatenation for markup.
Common defensive patterns include:
- Using a maintained implementation that applies correct encoding for text, attribute, URL, and script contexts
- Treating all dynamic metadata as untrusted unless its provenance and content are controlled
- Allowing only structured, schema-validated metadata values
- Avoiding HTML interpretation for metadata that should be plain text
- Using DOM or framework APIs that safely construct elements and attributes where applicable
- Applying restrictive Content Security Policy controls as defense in depth
- Limiting sensitive data exposed to rendered pages and reducing session privileges
Mitigation centers on using context-aware output encoding for every server-rendered HTML context and avoiding raw string concatenation for markup.
Common defensive patterns include:
- Using a maintained implementation that applies correct encoding for text, attribute, URL, and script contexts
- Treating all dynamic metadata as untrusted unless its provenance and content are controlled
- Allowing only structured, schema-validated metadata values
- Avoiding HTML interpretation for metadata that should be plain text
- Using DOM or framework APIs that safely construct elements and attributes where applicable
- Applying restrictive Content Security Policy controls as defense in depth
- Limiting sensitive data exposed to rendered pages and reducing session privileges
How teams detect issues like this
Detection approaches may include:
- Static analysis rules for raw HTML concatenation involving metadata or request-derived values
- Code review checks for serializers that reuse one escaping function across text, attribute, URL, and script contexts
- Tests that place boundary characters and markup-like input in every dynamic metadata field
- Server-rendered output inspection to verify that untrusted values remain encoded in their intended contexts
- Policy enforcement requiring context-aware templating or framework-safe rendering APIs
- Automated security review tools that identify unescaped interpolation into HTML responses
Detection approaches may include:
- Static analysis rules for raw HTML concatenation involving metadata or request-derived values
- Code review checks for serializers that reuse one escaping function across text, attribute, URL, and script contexts
- Tests that place boundary characters and markup-like input in every dynamic metadata field
- Server-rendered output inspection to verify that untrusted values remain encoded in their intended contexts
- Policy enforcement requiring context-aware templating or framework-safe rendering APIs
- Automated security review tools that identify unescaped interpolation into HTML responses
