This update for MozillaThunderbird to version 52.3 fixes security issues and bugs.
    
The following vulnerabilities were fixed:

- CVE-2017-7798: XUL injection in the style editor in devtools
- CVE-2017-7800: Use-after-free in WebSockets during disconnection
- CVE-2017-7801: Use-after-free with marquee during window resizing
- CVE-2017-7784: Use-after-free with image observers
- CVE-2017-7802: Use-after-free resizing image elements
- CVE-2017-7785: Buffer overflow manipulating ARIA attributes in DOM
- CVE-2017-7786: Buffer overflow while painting non-displayable SVG
- CVE-2017-7753: Out-of-bounds read with cached style data and pseudo-elements#
- CVE-2017-7787: Same-origin policy bypass with iframes through page reloads
- CVE-2017-7807: Domain hijacking through AppCache fallback
- CVE-2017-7792: Buffer overflow viewing certificates with an extremely long OID
- CVE-2017-7804: Memory protection bypass through WindowsDllDetourPatcher
- CVE-2017-7791: Spoofing following page navigation with data: protocol and modal alerts
- CVE-2017-7782: WindowsDllDetourPatcher allocates memory without DEP protections
- CVE-2017-7803: CSP containing 'sandbox' improperly applied
- CVE-2017-7779: Memory safety bugs fixed in Firefox 55 and Firefox ESR 52.3

The following bugs were fixed:

- Unwanted inline images shown in rogue SPAM messages
- Deleting message from the POP3 server not working when maildir storage was used
- Message disposition flag (replied / forwarded) lost when reply or forwarded message
  was stored as draft and draft was sent later
- Inline images not scaled to fit when printing
- Selected text from another message sometimes included in a reply
- No authorisation prompt displayed when inserting image into email body although
  image URL requires authentication
- Large attachments taking a long time to open under some circumstances