CVE-2020-15179 [High] | XSS in Scratchsig

The ScratchSig extension for MediaWiki before version 1.0.1 allows stored Cross-Site Scripting. Using <script> tag inside <scratchsig> tag, attackers with edit permission can execute scripts on visitors' browser. With MediaWiki JavaScript API, this can potentially lead to privilege escalation and/or account takeover. This has been patched in release 1.0.1. This has already been deployed to all Scratch Wikis. No workarounds exist other than disabling the extension completely.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.43%	1.22%	+0.79%
2	2025-03-30	0.34%	0.43%	+0.10%
3	2025-03-29	—	0.34%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.43%

1.22%

+0.79%

2025-03-30

0.34%

0.43%

+0.10%

2025-03-29

—

0.34%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.0	3.1	HIGH	`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.3	6.0	[email protected]
9.0	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.3	6.0	[email protected]
4.6	2.0	MEDIUM	`AV:N/AC:H/Au:S/C:P/I:P/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:H) Exploitation requires uncommon or highly specific conditions. Authentication (AU:S) A single authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	3.9	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.0

3.1

HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.3

6.0

[email protected]

9.0

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.3

6.0

[email protected]

4.6

2.0

MEDIUM

AV:N/AC:H/Au:S/C:P/I:P/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:H): Exploitation requires uncommon or highly specific conditions.
Authentication (AU:S): A single authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

3.9

6.4

[email protected]

Affected software / configurations for CVE-2020-15179

Vendor	Product	Version	Raw CPE
scratch-wiki	scratchsig	< 1.0.1	cpe:2.3:a:scratch-wiki:scratchsig::::::mediawiki::*

References for CVE-2020-15179

URL	Tags
https://github.com/InternationalScratchWiki/wiki-scratchsig/commit/4160a39a20eebeb63a59eb7597a91b961eca6388	Patch Third Party Advisory
https://github.com/InternationalScratchWiki/wiki-scratchsig/security/advisories/GHSA-gp9v-pg9f-vmp6	Third Party Advisory

URL

CVE-2020-15179 | HTML Injection in ScratchSig

Exploit prediction scoring system (EPSS) score for CVE-2020-15179

Common vulnerability scoring system (CVSS) metrics for CVE-2020-15179

Weakness enumeration for CVE-2020-15179

Affected software / configurations for CVE-2020-15179

References for CVE-2020-15179