Security readout for executives and security teams
Plain-English summary
A WordPress plugin called Flickr Gallery (versions 1.5.2 and older) has a critical flaw that lets anyone on the internet take control of a vulnerable site without logging in. Wordfence reported attackers actively used this in 2017 to plant backdoors. If your site uses this plugin, treat it as already at risk.
Executive priority
Treat as urgent. This is a critical, internet-exploitable flaw with confirmed historical mass exploitation. Any site still running the plugin should be remediated today and assessed for prior compromise.
Technical view
The plugin deserializes attacker-controlled input from the `pager` parameter, enabling unauthenticated PHP Object Injection (CWE-502). Per Wordfence, attackers leveraged the WP_Theme() class as a gadget to drop backdoors. CVSS 9.8 reflects network-reachable, no-auth, no-interaction exploitation with full confidentiality, integrity, and availability impact.
Likely exposure
Any WordPress site running Flickr Gallery <= 1.5.2 with the plugin endpoint reachable from the internet. The plugin appears abandoned, so most surviving installations are likely still vulnerable. Sources do not confirm a fixed release version.
Exploitation context
Wordfence documented in-the-wild exploitation in October 2017 as one of three zero-days hitting WordPress sites, with attackers using the bug to install persistent backdoors. CISA KEV does not list this CVE, but cited vendor reporting confirms historical active exploitation.
Researcher notes
CWE-502 deserialization gadget chain via WP_Theme() as cited by Wordfence. The CVE record lists `versions:["0"]` with `defaultStatus: unaffected`, which is ambiguous; the WordPress.org plugin trac changeset 1737576 likely contains the upstream fix. Validate against that changeset to determine the true patched version before clearing assets.
Mitigation direction
- Deactivate and remove the Flickr Gallery plugin from all WordPress sites immediately.
- Block requests containing the `pager` parameter to plugin endpoints at the WAF or reverse proxy.
- Check vendor or WordPress.org guidance for any patched release before reinstating the plugin.
- Assume compromise on long-running installs and rotate WordPress and database credentials.
- Engage incident response to hunt for webshells and unauthorized admin users.
Validation and detection
- Inventory WordPress sites and confirm whether `flickr-gallery` is installed and its version.
- Review web server and WAF logs for suspicious `pager` parameter values containing serialized PHP objects.
- Audit `wp-content` for unexpected PHP files, modified theme files, and rogue admin accounts.
- Compare core, plugin, and theme file hashes against known-good baselines.
- Check outbound connections and scheduled tasks for backdoor callbacks.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2017-20207 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.wordfence.com/threat-intel/vulnerabilities/id/b52ae51d-7b9a-4047-82bf-723ea87d2375?source=cveCVE reference
- https://www.wordfence.com/blog/2017/10/3-zero-day-plugin-vulnerabilities-exploited-wild/CVE reference
- https://plugins.trac.wordpress.org/changeset/1737576/flickr-galleryCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.