{"id":"CVE-2021-32671","aliases":["EUVD-2021-1271","GHSA-5qjq-69w6-fg57"],"status":"published","title":"XSS vulnerability with translator","description":"Flarum is a forum software for building communities. Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2.","severity":{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.4,"percentile":0.9864,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-79"],"published":"2021-06-07T21:25:12Z","modified":"2026-10-20T10:54:42Z","fixes":[{"ecosystem":"Packagist","package":"flarum/core","fixed_in":["1.0.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"flarum/core","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.0"},{"last_affected":"1.0.1"},{"fixed":"1.0.2"}]}]},{"source":"osv","ecosystem":"Packagist","package":"flarum/core","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.0"},{"fixed":"1.0.2"}]}],"versions":["v1.0.0","v1.0.1"]}],"products":[{"vendor":"flarum","product":"core"},{"vendor":"flarum","product":"flarum"},{"vendor":"opnsense","product":"core"}],"references":[{"url":"https://github.com/flarum/core/security/advisories/GHSA-5qjq-69w6-fg57","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory","web"]},{"url":"https://github.com/flarum/core/commit/440bed81b8019dff00642c8f493b4909d505a28a","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web"]},{"url":"https://packagist.org/packages/flarum/core","tags":["x_refsource_MISC","x_transferred","Product","Third Party Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-32671","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-5qjq-69w6-fg57"}],"sources":{"cve":[{"id":"CVE-2021-32671","title":"XSS vulnerability with translator","description":"Flarum is a forum software for building communities. Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2.","status":"published","published":"2021-06-07T21:25:12Z","modified":"2024-08-03T23:25:31.102Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:33:06.658806Z"}],"euvd":[{"id":"EUVD-2021-1271","description":"Flarum is a forum software for building communities. Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2.","status":"published","published":"2021-06-07T21:25:12Z","modified":"2024-08-03T23:25:31Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-03T03:24:36.41075Z"}],"ghsa":[{"id":"GHSA-5qjq-69w6-fg57","title":"XSS vulnerability with translator","description":"Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented.\n\nThis allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user.\n\n### Impact\n\nAll Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted.\n\n### Patches\n\nThe vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2 using:\n\n```\ncomposer update --prefer-dist --no-dev -a -W\n```\n\nYou can then confirm you run the latest version using:\n\n```\ncomposer show flarum/core\n```\n\n### Workarounds\n\n__None.__\n\n### For more information\n\nFor any questions or comments on this vulnerability please visit https://discuss.flarum.org/d/27558.\n\nFor support questions create a discussion at https://discuss.flarum.org/t/support.\n\nA reminder that if you ever become aware of a security issue in Flarum, please report it to us privately by emailing security@flarum.org, and we will address it promptly.\n","status":"published","published":"2021-06-07T21:48:17Z","modified":"2023-02-01T05:05:51Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:36:35.781528Z"}],"nvd":[{"id":"CVE-2021-32671","description":"Flarum is a forum software for building communities. Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2.","status":"published","published":"2021-06-07T22:15:07.743Z","modified":"2026-06-17T03:53:23.417Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"secondary"},{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":4.3,"vector":"AV:N/AC:M/Au:N/C:N/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:06:54.439974Z"}],"osv":[{"id":"CVE-2021-32671","description":"Flarum is a forum software for building communities. Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2.","status":"published","published":"2021-06-07T22:15:07.743Z","modified":"2026-10-20T10:54:42.084367793Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:19.793849Z"},{"id":"GHSA-5qjq-69w6-fg57","title":"XSS vulnerability with translator","description":"Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented.\n\nThis allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as \u003cscript\u003ealert('test')\u003c/script\u003e resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user.\n\n### Impact\n\nAll Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted.\n\n### Patches\n\nThe vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2 using:\n\n```\ncomposer update --prefer-dist --no-dev -a -W\n```\n\nYou can then confirm you run the latest version using:\n\n```\ncomposer show flarum/core\n```\n\n### Workarounds\n\n__None.__\n\n### For more information\n\nFor any questions or comments on this vulnerability please visit https://discuss.flarum.org/d/27558.\n\nFor support questions create a discussion at https://discuss.flarum.org/t/support.\n\nA reminder that if you ever become aware of a security issue in Flarum, please report it to us privately by emailing security@flarum.org, and we will address it promptly.\n","status":"published","published":"2021-06-07T21:48:17Z","modified":"2026-07-08T06:27:58.764355668Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:46:38.553953Z"}]}}