CVE-2020-15139

HIGHNVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under NVD CVSS v3. EPSS exploit probability: 1.3% (69th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1.3%CVSS: 8.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

In MyBB before version 1.8.24, the custom MyCode (BBCode) for the visual editor doesn't escape input properly when rendering HTML, resulting in a DOM-based XSS vulnerability. The weakness can be exploited by pointing a victim to a page where the visual editor is active (e.g. as a post or Private Message) and operates on a maliciously crafted MyCode message. This may occur on pages where message content is pre-filled using a GET/POST parameter, or on reply pages where a previously saved malicious message is quoted. After upgrading MyBB to 1.8.24, make sure to update the version attribute in the codebuttons template for non-default themes to serve the latest version of the patched jscripts/bbcodes_sceditor.js file.

CVSS v3
8.8
EG Score
8.8HIGHmedium confidence
EG Risk
45
EG Risk 45/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation1% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
1.3%
EPSS %ILE
69th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 10, 2020

Last Modified

November 21, 2024

Advisory Details (3)

Auto-updated Aug 20, 2026
Patch available. Sources: github_commit, github.
generic

Version 1.8.24 - MyBB

https://mybb.com/versions/1.8.24/
github Patch Available

MyCode message formatting XSS in visual editor · Advisory · mybb/mybb · GitHub

https://github.com/mybb/mybb/security/advisories/GHSA-37h7-vfv6-f8rj
github_commit Patch Available

commit 37ad29dcd254 (mybb/mybb)

Patch available: mybb/mybb mybb_1824 (contains commit 37ad29dcd254)

https://github.com/mybb/mybb/commit/37ad29dcd25489a37bdd89ebac761f22492558b0

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 30× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 171 total refreshes for this CVE.

  1. 2026-10-05 17:39 UTCEPSS rescore
  2. 2026-10-04 23:18 UTCEPSS rescore
  3. 2026-10-03 14:22 UTCEPSS rescore
  4. 2026-10-02 16:22 UTCEPSS rescore
  5. 2026-09-30 15:12 UTCEG score recompute
  6. 2026-09-30 14:59 UTCEPSS rescore
  7. 2026-09-27 13:40 UTCEPSS rescore
  8. 2026-09-26 18:33 UTCOSV refresh
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  1. 2026-09-10 09:29 UTCEPSS rescore
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  3. 2026-09-07 15:57 UTCEPSS rescore
  4. 2026-09-07 04:18 UTCOSV refresh
  5. 2026-09-06 13:44 UTCEPSS rescore
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  16. 2026-08-21 23:45 UTCEPSS rescore
  17. 2026-08-20 22:52 UTCEPSS rescore
  18. 2026-08-20 14:01 UTCOSV refresh
  19. 2026-08-19 17:00 UTCEPSS rescore
  20. 2026-08-18 13:44 UTCEPSS rescore
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  25. 2026-08-13 21:57 UTCEPSS rescore
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  27. 2026-08-09 13:43 UTCEPSS rescore
  28. 2026-08-08 16:33 UTCEPSS rescore
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  30. 2026-08-06 13:43 UTCEPSS rescore
  31. 2026-08-05 19:14 UTCEPSS rescore
  32. 2026-08-05 09:11 UTCOSV refresh
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  45. 2026-07-24 14:14 UTCEPSS rescore
  46. 2026-07-23 14:15 UTCEPSS rescore
  47. 2026-07-23 14:15 UTCEPSS rescore
  48. 2026-07-23 01:49 UTCEG score recompute
  49. 2026-07-22 22:35 UTCEG score recompute
  50. 2026-07-22 14:05 UTCEPSS rescore
  51. 2026-07-21 15:22 UTCEPSS rescore
  52. 2026-07-21 15:22 UTCEPSS rescore
  53. 2026-07-20 17:04 UTCEPSS rescore
  54. 2026-07-20 17:04 UTCEPSS rescore
  55. 2026-07-19 14:28 UTCEPSS rescore
  56. 2026-07-19 07:52 UTCOSV refresh
  57. 2026-07-19 02:26 UTCEPSS rescore
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  70. 2026-07-09 19:07 UTCEPSS rescore
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  72. 2026-07-07 13:43 UTCEPSS rescore
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  74. 2026-07-06 16:25 UTCEPSS rescore
  75. 2026-07-06 16:25 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2020-15139?
CVE-2020-15139 is a high vulnerability published on August 10, 2020. In MyBB before version 1.8.24, the custom MyCode (BBCode) for the visual editor doesn't escape input properly when rendering HTML, resulting in a DOM-based XSS vulnerability. The weakness can be exploited by pointing a victim to a page where the visual editor is active (e.g. as a post or Private…
When was CVE-2020-15139 disclosed?
CVE-2020-15139 was first published on August 10, 2020, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-15139 actively exploited?
CVE-2020-15139 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.3% probability of exploitation in the next 30 days (69th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2020-15139?
CVE-2020-15139 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2020-15139?
A fix for CVE-2020-15139 is available: update to the fixed version the vendor names in its advisory.

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