Intlify Vue I18n's escapeParameterHtml does not prevent DOM-based XSS via tag attributes like onerror

Vue I18n is the internationalization plugin for Vue.js. The escapeParameterHtml: true option in Vue I18n is designed to protect against HTML/script injection by escaping interpolated parameters. However, starting in version 9.0.0 and prior to versions 9.14.5, 10.0.8, and 11.1.0, this setting fails to prevent execution of certain tag-based payloads, such as <img src=x onerror=...>, if the interpolated value is inserted inside an HTML context using v-html. This may lead to a DOM-based XSS vulnerability, even when using escapeParameterHtml: true, if a translation string includes minor HTML and is rendered via v-html. Versions 9.14.5, 10.0.8, and 11.1.0 contain a fix for the issue.

Vue I18n is the internationalization plugin for Vue.js. The escapeParameterHtml: true option in Vue I18n is designed to protect against HTML/script injection by escaping interpolated parameters. However, starting in version 9.0.0 and prior to versions 9.14.5, 10.0.8, and 11.1.0, this setting fails to prevent execution of certain tag-based payloads, such as <img src=x onerror=...>, if the interpolated value is inserted inside an HTML context using v-html. This may lead to a DOM-based XSS vulnerability, even when using escapeParameterHtml: true, if a translation string includes minor HTML and is rendered via v-html. Versions 9.14.5, 10.0.8, and 11.1.0 contain a fix for the issue.

Vue I18n is the internationalization plugin for Vue.js. The escapeParameterHtml: true option in Vue I18n is designed to protect against HTML/script injection by escaping interpolated parameters. However, starting in version 9.0.0 and prior to versions 9.14.5, 10.0.8, and 11.1.0, this setting fails to prevent execution of certain tag-based payloads, such as <img src=x onerror=...>, if the interpolated value is inserted inside an HTML context using v-html. This may lead to a DOM-based XSS vulnerability, even when using escapeParameterHtml: true, if a translation string includes minor HTML and is rendered via v-html. Versions 9.14.5, 10.0.8, and 11.1.0 contain a fix for the issue.

### Summary The escapeParameterHtml: true option in Vue I18n is designed to protect against HTML/script injection by escaping interpolated parameters. However, this setting fails to prevent execution of certain tag-based payloads, such as `<img src=x onerror=...>`, if the interpolated value is inserted inside an HTML context using v-html. This may lead to a DOM-based XSS vulnerability, even when using escapeParameterHtml: true, if a translation string includes minor HTML and is rendered via v-html. ### Details When escapeParameterHtml: true is enabled, it correctly escapes common injection points. However, it does not sanitize entire attribute contexts, which can be used as XSS vectors via: `<img src=x onerror=alert(1)> ` ### PoC In your Vue I18n configuration: ``` const i18n = createI18n({ escapeParameterHtml: true, messages: { en: { vulnerable: 'Caution: <img src=x onerror="{payload}">' } } }); ``` Use this interpolated payload: `const payload = '<script>alert("xss")</script>';` Render the translation using v-html (even not using v-html): `<p v-html="$t('vulnerable', { payload })"></p> ` Expected: escaped content should render as text, not execute. Actual: script executes in some environments (or the payload is partially parsed as HTML). ### Impact This creates a DOM-based Cross-Site Scripting (XSS) vulnerability despite enabling a security option (escapeParameterHtml) .