CVE-2020-8291Network attack vector

Cross-site scripting via unescaped attachment fields

Published Oct 18, 2021 · Updated Aug 4, 2024

Cross-site scripting in Rocket.Chat before 3.9 allows remote attackers to execute scripts in a user's browser through a crafted link preview. The message-attachment renderField helper treated field values and types as preformatted HTML and inserted them into a div without escaping. Exploitation requires a user to view the generated preview; execution remains in that user's browser context and can read or alter accessible workspace data.

CVSS severity6.1
Medium
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Rocket.Chat before 3.9 allows remote attackers to execute scripts in a user's browser through a crafted link preview. The message-attachment renderField helper treated field values and types as preformatted HTML and inserted them into a div without escaping. Exploitation requires a user to view the generated preview; execution remains in that user's browser context and can read or alter accessible workspace data.

The record

CVE
CVE-2020-8291
Published
Oct 18, 2021
Updated
Aug 4, 2024
Vendor
Rocket.Chat Technologies Corp.
Product
Rocket.Chat
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Fixed versions: 3.10, 3.9.4, 3.8.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rocket.Chat Technologies Corp. · Rocket.Chatversion=Fixed versions: 3.10, 3.9.4, 3.8.5

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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